nellcor oximetro portatil servicio

Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician.

To contact Mallinckrodt’s representative: In the United States, call 1.800.635.5267 or 314.654.2000; outside the United States, callyour local Mallinckrodt representative.

0123

2001 Mallinckrodt Inc. All Rights reserved. 062153C-0701

SERVICE MANUAL

N-20PA Portable Pulse Oximeter

Nellcor Puritan Bennett Inc. is a wholly owned subsidiary of Mallinckrodt Inc. Nellcor and Nellcor Puritan Bennett aretrademarks of Mallinckrodt Inc.

To obtain information about a warranty, if any, for this product, contact Nellcor Technical Services or your local Nellcorrepresentative.

Covered by one or more of the following U.S. Patents and corresponding foreign patents: 4,621,643; 4,685,464; 4,700,708;and 4,770,179

Nellcor Puritan Bennett Inc.4280 Hacienda DrivePleasanton, CA 94588 USATelephone Toll Free 1.800.NELLCOR

Tyco Healthcare UK LTDFareham RoadGosportPO13 0ASU.K.Tel: +44.1329.224000

iii

CONTENTS

Contents................................................................................................................................................................... iii

Figures..................................................................................................................................................................... iv

Tables ....................................................................................................................................................................... v

SECTION 1: Introduction....................................................................................................................................1-1

1.1 Manual Overview..........................................................................................................................................1-1

1.2 Warnings, Cautions, and Notes.....................................................................................................................1-1

1.3 Description of the N-20PA Portable Pulse Oximeter ...................................................................................1-1

SECTION 2: Routine Maintenance.....................................................................................................................2-1

2.1 Overview .......................................................................................................................................................2-1

2.2 Cleaning........................................................................................................................................................2-1

2.3 Periodic Safety and Functional Checks ........................................................................................................2-1

2.4 Battery...........................................................................................................................................................2-1

SECTION 3: Performance Verification...............................................................................................................3-1

3.1 Introduction ..................................................................................................................................................3-1

3.2 Required Tools and Equipment.....................................................................................................................3-1

3.3 Performance Tests ........................................................................................................................................3-1

SECTION 4: Troubleshooting .............................................................................................................................4-1

4.1 Introduction ..................................................................................................................................................4-1

4.2 How to Use This Section ...............................................................................................................................4-1

4.3 Who Should Perform Repairs .......................................................................................................................4-1

4.4 Replacement Level Supported.......................................................................................................................4-1

4.5 Obtaining Replacement Parts .......................................................................................................................4-1

4.6 Troubleshooting Guide .................................................................................................................................4-1

SECTION 5: Disassembly Guide .........................................................................................................................5-1

5.1 Introduction ..................................................................................................................................................5-1

5.2 Beginning Disassembly.................................................................................................................................5-1

5.3 Disassemblying the Printer/Flex Circuit Assembly.......................................................................................5-4

SECTION 6: Spare Parts .....................................................................................................................................6-1

6.1 Introduction ..................................................................................................................................................6-1

6.2 Spare Parts List ............................................................................................................................................6-1

SECTION 7: Packing for Shipment ....................................................................................................................7-1

7.1 General Instructions .....................................................................................................................................7-1

CONTENTS

iv

7.2 Repacking in Original Carton ......................................................................................................................7-1

7.3 Repacking in a Different Carton...................................................................................................................7-1

SECTION 8: Specifications..................................................................................................................................8-1

8.1 Performance..................................................................................................................................................8-1

8.2 Alarms...........................................................................................................................................................8-1

8.3 Electrical.......................................................................................................................................................8-2

8.4 Environmental...............................................................................................................................................8-2

8.5 Physical.........................................................................................................................................................8-3

SECTION 9: Technical Supplement....................................................................................................................9-1

9.1 Introduction ..................................................................................................................................................9-1

9.2 Functional Overview.....................................................................................................................................9-1

9.3 Definition of Terms .......................................................................................................................................9-5

9.4 Overall Block Diagram.................................................................................................................................9-6

9.5 SpO2 Analog Circuitry .................................................................................................................................9-6

9.6 Digital Circuitry..........................................................................................................................................9-12

9.7 Circuit Illustrations.....................................................................................................................................9-31

FIGURES

Figure 5-1: Sensor Lock, Printer, Paper, and Battery Access Doors.........................................................................5-1

Figure 5-2: N-20PA Covers with the PCB and Display Assembly ............................................................................5-2

Figure 5-3: Main, Auxiliary, and Display PCB Assembly .........................................................................................5-3

Figure 5-4: Printer and Flex Circuit Assembly..........................................................................................................5-4

Figure 9-1: Overall Block Diagram...........................................................................................................................9-1

Figure 9-2: SpO2 Analog Block Diagram..................................................................................................................9-2

Figure 9-3: N-20PA Hardware Block Diagram..........................................................................................................9-3

Figure 9-4: Power Supply Block Diagram .................................................................................................................9-4

Figure 9-5: Display Control Block Diagram ..............................................................................................................9-4

Figure 9-6: Printer Control Block Diagram................................................................................................................9-5

Figure 9-7: SpO2 Analog Circuitry Block Diagram...................................................................................................9-7

Figure 9-9: Differential Synchronous Demodulation Circuit .....................................................................................9-9

Figure 9-11: Variable Gain Circuit ..........................................................................................................................9-10

Figure 9-12: Filtering Circuit ..................................................................................................................................9-11

Figure 9-14: Digital Circuitry Block Diagram .........................................................................................................9-13

Figure 9-16: Address Demultiplexing Circuit ..........................................................................................................9-15

Figure 9-17: Address Decoding Circuit ...................................................................................................................9-16

CONTENTS

v

Figure 9-18: CPU Memory Circuit .........................................................................................................................9-17

Figure 9-19: Input Port Circuit.................................................................................................................................9-18

Figure 9-21: Real-Time Clock Circuit .....................................................................................................................9-19

Figure 9-22: Audio Output Circuit ...........................................................................................................................9-20

Figure 9-24: User Controls Circuit...........................................................................................................................9-23

Figure 9-27: Analog Reference Voltage Circuit.......................................................................................................9-26

Figure 9-28: Ambient Light Circuit..........................................................................................................................9-27

Figure 9-29: Ambient Temperature Circuit..............................................................................................................9-27

Figure 9-30: Battery Voltage Circuit........................................................................................................................9-28

Figure 9-31: Battery Type Circuit ...........................................................................................................................9-28

Figure 9-8: LED Drive Circuit ................................................................................................................................9-33

Figure 9-10: N-20PA HSO Timing Diagram ..........................................................................................................9-35

Figure 9-13: AC Variable Gain Control Circuit......................................................................................................9-37

Figure 9-15: CPU Circuit ........................................................................................................................................9-39

Figure 9-20: Output Port Circuit .............................................................................................................................9-41

Figure 9-23: Display Control Circuit ......................................................................................................................9-43

Figure 9-25: Power Supply Circuit .........................................................................................................................9-45

Figure 9-26: Power Control Circuit.........................................................................................................................9-47

Figure 9-32: Printer Interface Circuit......................................................................................................................9-49

Figure 9-33: Printer Flex Circuit .............................................................................................................................9-51

Figure 9-34: N-20PA Main PCB Schematic Diagram ............................................................................................9-53

Figure 9-35: N-20PA Auxiliary PCB Schematic Diagram......................................................................................9-55

Figure 9-36: N-20PA Flex Circuit Schematic Diagram ..........................................................................................9-57

TABLES

Table 4-1 : Troubleshooting the N-20PA..................................................................................................................4-2

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1-1

SECTION 1: INTRODUCTION

1.1 Manual Overview

1.2 Warnings, Cautions, and Notes

1.3 Description of the N-20PA Portable Pulse Oximeter

1.1 MANUAL OVERVIEW

This manual contains information for servicing the N-20PA portable pulseoximeter. Only qualified service personnel should service this product. Beforeservicing the device, read the operator’s manual carefully for a thoroughunderstanding of its operation.

1.2 WARNINGS, CAUTIONS, AND NOTES

This manual uses three terms that are important for proper operation of thedevice: Warning, Caution, and Note.

1.2.1 Warning

A warning precedes an action that may result in injury or death to the patient oruser. Warnings are boxed and highlighted in boldface type.

1.2.2 Caution

A caution precedes an action that may result in damage to, or malfunction of, thedevice. Cautions are highlighted in boldface type.

1.2.3 Note

A note gives information that requires special attention.

1.3 DESCRIPTION OF THE N-20PA PORTABLE PULSE OXIMETER

The Nellcor

N-20PA portable pulse oximeter provides noninvasivemeasurement of, and continuous information about, the percent of oxygenatedhemoglobin compared with total hemoglobin and pulse rate. A pulse amplitudeindicator provides a qualitative indication of pulse activity and patient perfusion.Patients are connected to the instrument by a Nellcor sensor. The sensor LEDsare driven by the SpO2 analog section, which also conditions the incomingsignals, and provides CPU-adjustable gain stages. The N-20PA CPU measuresthe sensor’s analog outputs, continually controls the signal gain, and calculatesSpO2 and pulse rate.

The N-20PA is automatically calibrated each time it is switched on, andwhenever a new sensor is connected; it sets sensor-specific calibrationcoefficients by reading a calibration resistor in the sensor. Also, the intensity ofthe sensor’s light sources are adjusted automatically to compensate fordifferences in tissue thickness and darkness.

Section 1: Introduction

1-2

Standard user controls consist of a measure button and a check-battery button.The measure button signals the power control circuit to switch on the powersupply. The power supply then provides regulated power to the unit. Once poweris on, both the measure and check battery buttons are read by the CPU for usercommands.

The N-20PA printer provides a hard copy of acquired patient measurements.The printer circuit includes three user control buttons: ON (on/off), ADV(advance), and D/D (day/date). In addition, an ambient temperature sensor isused with the battery voltage input to control printout quality.

2-1

SECTION 2: ROUTINE MAINTENANCE

2.1 Overview

2.2 Cleaning

2.3 Periodic Safety and Functional Checks

2.4 Batteries

2.1 OVERVIEW

The N-20PA requires no routine maintenance, routine service, or calibration. Ifservice is necessary, contact qualified service personnel or your localMallinckrodt representative. Use only Mallinckrodt-approved test equipmentwhen running a performance test on the N-20PA. The user's institution, local ornational agencies, or both may also require testing.

2.2 CLEANING

Dampen a cloth with a commercial, nonabrasive cleaner, and lightly wipe thesurfaces of the N-20PA. Do not spray or pour liquid on the instrument oraccessories. Do not allow liquid to contact connectors, switches, or openings inthe chassis.

2.3 PERIODIC SAFETY AND FUNCTIONAL CHECKS

The following checks should be performed at least every 2 years by a qualifiedservice technician.

Inspect the exterior of the N-20PA for damage.

Inspect safety labels for legibility. If the labels are not legible, contact MallinckrodtTechnical Services Department or your local Mallinckrodt representative.

2.4 BATTERY

When the N-20PA is going to be stored for 3 months or more, remove the batteryprior to storage. To replace or remove the battery, refer to Section 5,Disassembly Guide.

3-1

SECTION 3: PERFORMANCE VERIFICATION

3.1 Introduction

3.2 Required Tools and Equipment

3.3 Performance Tests

3.1 INTRODUCTION

This section describes performance verification and safety testing for the NellcorN-20PA pulse oximeter (monitor) and all options, following troubleshooting andrepairs.

The tests can be performed without removing the monitor cover. All tests exceptBattery Operation must be performed before the monitor is returned to the user.

If the monitor fails to perform as specified in any test, repairs must correct thediscrepancy before the monitor is returned to the user.

The N-20PA is powered by alkaline batteries. The N-20PA design includesbuilt-in electrical isolation; no ground resistance or current leakage testing isrequired. In addition, the N-20PA requires no calibration.

3.2 REQUIRED TOOLS AND EQUIPMENT

Durasensor Nellcor DS-100A

Oxisensor II Nellcor D-25

Tester, Pulse Oximeter Nellcor SRC-2 or SRC-1

Variable DC power supply; 1 amp supply, voltage range 0-6 VDC

3.3 PERFORMANCE TESTS

The procedures required to verify correct monitor performance are listed below:

3.3.1 Battery Performance

3.3.2 Power-Up Performance

3.3.3 Hardware and Software Tests

3.3.4 Backlight Test

3.3.5 Low Battery Test

3.3.6 Printer Test

The N-20PA will operate in diagnostic mode in conjunction with the Nellcorpulse oximetry tester, model SRC-2 or SRC-1, to test instrument performance.The SRC-2 plugs into the DB-9 sensor connector and uses the instrument’spower supply and diagnostic software to test the display and the operation of theinstrument. Mallinckrodt recommends routine performance testing at 1-yearintervals. Refer to the SRC-2 operator’s manual for details on performancetesting with the SRC-2.

Performance Verification

3-2

To enter the diagnostic mode, connect the SRC-2 to the N-20PA while theoximeter is off; then, turn the oximeter on. While in the diagnostic mode, a “d”is displayed in the leftmost segment of the display. Note: No alarms sound whilein the diagnostic mode. Note also that, if the SRC-2 is disconnected while theN-20PA is in diagnostic mode, the N-20PA shuts off automatically.

3.3.1 Battery Performance

This test is provided to verify that the monitor will operate for the periodspecified.

The monitor is specified to operate on battery power as follows:

N-20/PA (with printer) 32 hours with Alkaline batteries.

This test requires a new set of batteries. Note that the batteries must be replacedafter the test.

1. Connect the Nellcor SRC-2 pulse oximeter tester to the monitor.

2. Set the switches on the SRC-2 as follows:

Switch Setting

RATE 38

LIGHT LOW

MODULATION LOW

RCAL/MODE RCAL 63/LOCAL

3. Momentarily press the MEASURE button, and then verify the followingpower-up sequence:

a. All indicators--OXYGEN SATURATION, PULSE RATE, PULSESEARCH, LOW BATTERY, and the PULSE BARS--light for a fewseconds. Verify that the OXYGEN SATURATION and PULSE RATEdisplays indicate "888."

b. The OXYGEN SATURATION display momentarily indicates themonitor 3-digit software version. The other displays are not lit.

Software versions may vary depending on the date of manufacture.

The N-20PA will display the letters “PA” in the PULSE RATE displaywhile the software version is being displayed in the OXYGENSATURATION display.

c. The OXYGEN SATURATION display momentarily indicates the letters”tSt” and the monitor sounds a single tone. The other displays are not lit.“tSt” verifies that the monitor recognizes that a tester is connected.

d. The OXYGEN SATURATION and PULSE RATE displays indicate“0,” the PULSE SEARCH indicator is flashing, and the PULSE BARwill start to register the simulated pulse.

e. After a few beats, a pulse tone will be heard, and the PULSE SEARCHindicator will turn off. The OXYGEN SATURATION display indicatesbetween 79 and 83 and the PULSE RATE display indicates between 37and 39.

The N-20PA will indicate a “d” in the most significant digit (MSD) ofthe OXYGEN SATURATION display when the SRC-2 is connected.


3-3

4. The monitor must operate for at least 37 hours with no printer activity.

5. Verify that the LOW BATTERY indicator lights sometime after 35 hours ofoperation.

6. Verify that the LOW BATTERY indicator starts flashing after 36 hours ofoperation.

7. Verify that the monitor turns off approximately 1 hour after the LOWBATTERY indicator starts flashing.

8. Allow the monitor to continue operation until power-down due to lowbattery.

3.3.2 Power-up Performance

Monitors with the same software must demonstrate identical startup routines.

The power-up tests verify the following monitor functions:

3.3.2.1 Power-On Self-Test

3.3.2.2 Adult Defaults and Alarm Limit Ranges

3.3.2.3 Neonate Defaults and Alarm Limit Ranges

3.3.2.1 Power-On Self-Test

1. Place a new set of batteries in the monitor.

2. Do not connect a sensor or SRC-2 to the monitor.

3. Momentarily press the MEASURE button, and verify the following power-up sequence:


b. The OXYGEN SATURATION display momentarily indicates themonitor 3 -digit software version. The other displays are not lit.

Note: Software versions may vary depending on the manufacture date.

Note: The N-20PA will display the letters “PA” in the PULSE RATE displaywhile the software version is being dispalyed in the OXYGENSATURATION display.

c. The OXYGEN SATURATION and PULSE RATE display dashes “-” ineach window, the monitor sounds a single tone, and the PULSESEARCH indicator is flashing. The other displays are not lit.

4. Verify that the monitor automatically turns off after 60 seconds.

Change the SRC-2 to the switch configurations shown below, and verify monitoroperation using the chart shown below.


3-4

SRC-2 Settings Monitor Indications

RATE LIGHT MODULATION SpO2 PR

112 HIGH1 HIGH 81+ 2 112+ 2% (110 - 114)

201 LOW LOW 81+ 2 201+ 3% (195 - 207)

201 LOW HIGH 81+ 2 201+ 3% (195 - 207)

3.3.2.2 Adult Defaults and Alarm Limit Ranges

The following procedure will allow verification of the monitor’s adult factorydefaults, adjusting those defaults, and automatic reset to factory defaults.

1. Place a new set of batteries in the monitor.

2. Connect the DS-100A sensor to the monitor and place the sensor on a livesubject.

3. Press the MEASURE button, and verify the following power-up sequence:



Note: Software versions may vary depending on the date of manufacture.

Note: The monitor will display the letters “PA” in the PULSE RATE displaywhile the software version is being displayed in the OXYGENSATURATION display.

c. The OXYGEN SATURATION and PULSE RATE display “0” in eachwindow, the monitor sounds a single tone, and the PULSE SEARCHindicator is lit. The other displays are not lit.

d. The monitor will begin to track the pulse and after a few beats willdisplay the subject’s Oxygen Saturation and Pulse Rate.

If the subject’s OXYGEN SATURATION is below 91, select anothersubject to facilitate the test procedure as written.

4. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the “dashes” are flashing. The “H”indicates that the High Alarm Limits can be set. The “dashes” in the SpO2display indicate that the present setting is the Adult Default of 100% andcannot be increased.


3-5

SpO2 %

/ min

- +

5. Press the PRINTER ON button and reduce the High Saturation Alarm limitbelow the live subject’s value; typically 90 will be sufficient.

6. Momentarily press the DAY/DATE button and verify that the “90” in theSpO2 display stops flashing and the “170” starts flashing.

7. Press the PRINTER PAPER ADVANCE button and increase the High RateAlarm limit to 190.

8. Momentarily press the DAY/DATE button; then verify that the followingdisplay is shown and that the “85” is flashing.

SpO2 %

/ min

- +

9. Press the PRINTER ON button, and reduce the Low Saturation Alarm limitto 80.

10. Momentarily press the DAY/DATA button, and verify that the “80” in theSpO2 display stops flashing and the “40” starts flashing.

11. Press the PRINTER ON button, and reduce the Low Rate Alarm limit to 30.

12. Momentarily press the DAY/DATE button and verify that the monitorreturns to the normal monitoring display and indicates the subject’ssaturation and pulse rate.

13. Verify that the monitor begins to alarm and that the SpO2 reading begins toflash.

14. Momentarily press the BATTERY TEST button, and verify that the alarmremains silent for 2 minutes and that the SpO2 reading continues to flash.

Note: The alarm may be silenced as necessary for remainder of the test.


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15. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the “90” is flashing.

SpO2 %

/ min

- +

16. Momentarily press the DAY/DATE button and verify that the “90” in theSpO2 display stops flashing and that the “190” Rate Default starts flashing.

17. Momentarily press the DAY/DATE button and verify that the followingdisplay is shown and that the “80 “ is flashing.

SpO2 %

/ min

- +

18. Momentarily press the DAY/DATE button and verify that the “80” in theSpO2 display stops flashing and that the “30” in the Rate Display startsflashing.

19. Momentarily press the DAY/DATE button and verify that the monitorreturns to the normal monitoring display and indicates the live subject’ssaturation and pulse rate.

20. Press the MEASURE button until the monitor turns off.


3-7


a. All indicators--OXYGEN SATURATION, PULSE RATE, PULSESEARCH, LOW BATTERY, and the PULSE BARS --light for a fewseconds. Verify that the OXYGEN SATURATION and PULSE RATEdisplays indicate "888."

b. The OXYGEN SATURATION display momentarily indicates themonitor 3-digit software version. The other displays are not lighted.

Note: Software versions may vary depending on the type of monitor and the dateof manufacture.

The monitor will display the letters PA in the PULSE RATE displaywhile the software version is being displayed in the OXYGENSATURATION display.

c. The OXYGEN SATURATION and PULSE RATE displays “0” in eachwindow, the monitor sounds a single tone and the PULSE SEARCHindicator is flashing. The other displays are not lit.


22. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the dashes (“-“) are flashing. Thisindicates the monitor has returned to the factory default settings.

SpO2 %

/ min

- +

23. Momentarily press the DAY/DATE button and verify that the dashes (“-“) inthe SpO2 display stop flashing and that the “170” Rate Default startsflashing.

24. Momentarily press the DAY/DATE button and verify that the followingdisplay is shown and that the “85” is flashing.


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SpO2 %

/ min

- +

25. Momentarily press the DAY/DATA button and verify that the “85” in theSpO2 display stops flashing and that the “40” Rate Default starts flashing.



3.3.2.3 Neonate Defaults and Alarm Limit Ranges

The following procedure will allow verification of the monitor NEONATALfactory defaults, adjusting those defaults, and automatic reset to factory Adultdefaults.

1. Place a set of batteries in the monitor. Verify that batteries are new.

2. Connect the DS-100A sensor to the monitor and place the sensor on alive subject (adult subject is OK for this procedure).

3. Press and hold the BATTERY TEST button and press the MEASUREbutton for at least 5 seconds, and then verify the following power-upsequence:

a. All indicators—OXYGEN SATURATION, PULSE RATE, PULSESEARCH, LOW BATTERY, and the PULSE BARS--light for a fewseconds. Verify that the OXYGEN SATURATION and PULSE RATEdisplays indicate "888."




c. The OXYGEN SATURATION and PULSE RATE displays “0” in eachwindow, the monitor sounds a single tone, and the PULSE SEARCHindicator is lit. The other displays are not lit.

An “n” will be displayed in the Most Significant Digit (MSD) of theSpO2 display, indicating the Neonatal mode.


3-9


4. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the “95” is flashing. The “H” indicatesthat the High Saturation Alarm Limit can be set.

SpO2 %

/ min

- +

5. Press the PRINTER ON button and reduce the High Saturation Alarm limitto 90.

6. Momentarily press the DAY/DATE button and verify that the “90” in theSpO2 display stops flashing and that the “190” starts flashing.

7. Press the PRINTER PAPER ADVANCE button and increase the High RateAlarm limit to 205.

8. Momentarily press the DAY/DATE button to verify that the followingdisplay is shown and that the “80” is flashing.

SpO2 %

/ min

- +

9. Press the PRINTER ON button and reduce the Low Saturation Alarm limitto 70.

10. Momentarily press the DAY/DATE button and verify that the “70” in theSpO2 display stops flashing and that the “90” starts flashing.

11. Press the PRINTER ON button and reduce the Low Rate Alarm limit to 80.


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13. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the “90” is flashing.

SpO2 %

/ min

- +

14. Momentarily press the DAY/DATE button and verify that the “90” in theSpO2 display stops flashing and that the “205” Rate Default starts flashing.

15. Momentarily press the DAY/DATE button and verify that the followingdisplay is shown and that the “70 “ is flashing.

SpO2 %

/ min

- +

16. Momentarily press the DAY/DATE button and verify that the “70” in theSpO2 display stops flashing and that the “80” in the Rate Display startsflashing.


18. Verify that the monitor begins to alarm and that the number representing thelive subject’s saturation and pulse rate begins to flash.


3-11

19. Momentarily press the BATTERY TEST button and verify that the alarmremains silent for 2 minutes and that the number representing the livesubject’s saturation and pulse rate continues to flash.

The alarm may be silenced as necessary for remainder of the test.







c. The OXYGEN SATURATION and PULSE RATE display dashes “0” ineach window, the monitor sounds a single tone, and the PULSESEARCH indicator is lit. The other displays are not lit.


22. Press and hold the BATTERY CHECK button and then momentarily pressthe DAY/DATE (D/D) button on the top of the monitor. Verify that thefollowing display is shown and that the “dashes” are flashing. This indicatesthe monitor has returned to the factory default settings.

SpO2 %

/ min

- +

23. Momentarily press the DAY/DATE button and verify that the “dashes” inthe SpO2 display stop flashing and that the “170” Rate Default startsflashing.

24. Momentarily press the DAY/DATE button, and verify that the followingdisplay is shown and that the “85” is flashing.


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SpO2 %

/ min

- +

25. Momentarily press the DAY/DATA button and verify that the “85” in theSpO2 display stops flashing and that the “40” Rate Default starts flashing.



3.3.3 Hardware and Software Tests

Hardware and software tests include the following:

3.3.3.1 Operation with a Pulse Oximeter Tester

3.3.3.2 Normal Operation

3.3.3.1 Operation with a Pulse Oximeter Tester

1. Connect the Nellcor SRC-2 pulse oximeter tester to the monitor.

2. Set the switches on the SRC-2 as follows:

Switch Setting

RATE 38

LIGHT LOW

MODULATION LOW

RCAL/MODE RCAL 63/LOCAL

3. Momentarily press the MEASURE button, and verify the following power-up sequence:

a. All indicators—OXYGEN SATURATION, PULSE RATE, PULSESEARCH, LOW BATTERY, and the PULSE BARS—light for a fewseconds. Verify that the OXYGEN SATURATION and PULSE RATEdisplays indicate "888."


3-13



The N-20PA will display the letters “PA” in the PULSE RATE displaywhile the software version is being displayed in the OXYGENSATURATION display.

c. The OXYGEN SATURATION display momentarily indicates the letters”tSt” and the monitor sounds a single tone. The other displays are not lit.“tSt” verifies that the monitor recognizes that a tester is connected.

d. The OXYGEN SATURATION and PULSE RATE displays indicate“0,” the PULSE SEARCH indicator is flashing, and the PULSE BARwill start to register the simulated pulse.

e. After a few beats a pulse tone will be heard, and the PULSE SEARCHindicator will turn off. The OXYGEN SATURATION display indicatesbetween 79 and 83 and the PULSE RATE display indicates between 37and 39.

The N-20PA will indicate a “d” in the most significant digit (MSD) ofthe OXYGEN SATURATION display when the SRC-2 is connected.

3.3.3.2 Normal Operation

These tests are an overall qualitative check of the system and requiresconnecting a live subject to the monitor.

1. Connect a DS-100A Sensor to monitor.

2. Place the DS-100A Sensor on the subject as recommended in the N-20PA Operator's Manual.

3. Press the MEASUREMENT button to turn on the monitor.

4. The monitor should stabilize on the subject's physiological signal inabout 10 to 15 seconds. Verify that the saturation value and pulse ratesare acceptable

3.3.4 Backlight Test

The electroluminescent backlight illuminates the display in three sections:

1. The main section, that is, the Oxygen Saturation and Pulse Rate displayfields, and the 14-segment pulse rate amplitude indicator;

2. The Low Battery indicator, and

3. Pulse Search indicators each have their own backlight. Each backlightflashes once during Power-On Self Test.

The ambient light detector is located underneath a small circular window in thetop right corner of the N-20PA display. Under low light conditions, the mainsection backlight is switched on. If a Low Battery and Pulse Search indicator islit, those individual backlights are also lit.


3-14

To test for proper operation of the display backlight, observe the N-20PA in adarkened room. If any backlight section is not working correctly, contactMallinckrodt’s Technical Services Department or your local Mallinckrodtrepresentative for assistance.

3.3.5 Low Battery Test

The N-20PA CPU monitors the battery voltage level and alerts the user via theLow Battery indicator when voltage is getting low. To test the proper functionof the Low Battery indicator, connect the N-20PA to an external variable DCpower supply.

Battery voltage levels described in this section are accurate; however, slightvariations may exist due to differences between batteries of differentmanufacturers. To that point, the N-20PA operates normally at voltages above4.0 VDC.

When the battery voltage drops below 4.05 VDC, the Low Battery indicator islit, and the two lowest segments of the battery level meter are lit (number ofsegments lit is dependent upon battery strength) when the battery-check button ispressed. When the voltage level drops below 4 VDC, the N-20PA continues todisplay Oxygen Saturation and Pulse Rate values, but the printer no longeroperates; otherwise, the N-20PA operates normally.

Battery voltage levels below 3.5 VDC cause the Low Battery indicator to beginflashing. When the battery-check button is pressed only the lowest segment ofthe Low Battery indicator will illuminate.

When the battery voltage level drops below 3.3 VDC, the N-20PA turns itselfoff.

Caution: If a sensor is attached, remove it prior to running the followingtest.

To test for proper function of the Low Battery indicator:

1. Switch off the N-20PA; open the battery door and remove the batteries.

2. Set the power supply voltage to 5 VDC, and connect the supply to thebattery contacts of the N-20PA.

Note: Ensure that polarity is correct.

3. Switch on the N-20PA; verify complete Power-On Self Test (the N-20PAshould operate normally).

4. Decrease the power supply voltage to 4.0 VDC or slightly below. The LowBattery indicator should illuminate and the lowest two segments of thebattery level meter should illuminate and printer operation should cease.

5. Decrease the power supply voltage to 3.5 VDC or slightly below. Thenpress the battery-check button; the Low Battery indicator should begin toflash and only the lowest segment of the battery level meter shouldilluminate.

6. Decrease the power supply voltage to below 3.2 VDC. The N-20PA shouldturn itself off immediately. Pressing the measure button should not turn theunit back on.


3-15

The Low Battery indicator test is now complete.

3.3.6 Printer Test

The SRC-2 tester can be used to test the operation of the N-20PA printer and theprinter’s user-control buttons. When an SRC-2 is plugged into the DB-9connector, the N-20PA acknowledges any button press with an immediate beepand the following display codes:

Button Press Display

On/Off 9O

battery check bAt

ON On

ADV Ad

D/D dd

combinations Err

1. Momentarily click the On/Off button: “9O” appears in (or shuts off) theOxygen Saturation display.

2. Press the battery-check button: “bAt” appears in the Oxygen Saturationdisplay.

3. Press the printer ON button: “On” appears in the Oxygen Saturation display.A printer test pattern prints out; the following is an approximate example ofthe test pattern:

Examine the test pattern to verify that all dots print with a uniform darkness.Overall printout darkness can be adjusted; to adjust printer darkness, seeparagraph 0. If printout darkness is either irregular or dots are missing, contactMallinckrodt’s Technical Services Department or your local Mallinckrodtrepresentative for assistance.

4. Press the printer ADV button: “Ad” appears in the Oxygen Saturationdisplay. The paper advances one line for each button press.

5. Press the printer D/D button: “dd” appears in the Oxygen Saturation display.

The SRC-2 printer test is now completed.


3-16

TEST RESULTS

Model: N-20PA Serial:_____________________________

Date:___________Customer Name:________________________________

Test # Description Pass Fail

3.3.1 Battery Performance ____ ____

3.3.2 Power-Up Performance ____ ____

3.3.2.1 Power-Up Self-Test ____ ____

3.3.2.2 Adult Defaults and Alarm Limit Ranges ____ ____

3.3.2.3 Neonate Defaults and Alarm Limit Ranges ____ ____

3.3.3 Hardware and Software Tests ____ ____

3.3.3.1 Operation with a Pulse Oximeter Tester ____ ____

3.3.3.2 Normal Operation ____ ____

3.3.4 Backlight Test ____ ____

3.3.5 Low Battery Test ____ ____

3.3.6 Printer Test ____ ____

I certify that the monitor listed in this form has successfully passed all of these tests.

Technician:_________________________________________________Date:____________

I certify that the above signed technician has performed the tests listed on this form and the monitorperforms satisfactorily.

Support CenterManager:___________________________________________________Date:____________

4-1

SECTION 4: TROUBLESHOOTING4.1 Introduction4.2 How to Use This Section4.3 Who Should Perform Repairs4.4 Replacement Level Supported4.5 Obtaining Replacement Parts4.6 Troubleshooting Guide

4.1 INTRODUCTION

This section explains how to identify and correct monitor difficulties andprovides procedures for common service-related activities, such as batteryreplacement, clearing paper jams, and adjusting printer darkness.

4.2 HOW TO USE THIS SECTION

Use this section in conjunction with Section 3, Performance Verification, andSection 6, Spare Parts. To remove and replace a part you suspect is defective,follow the instructions in Section 5, Disassembly Guide. The functional circuitanalysis, located in the Technical Supplement at the end of this manual, offersinformation on how the device functions, as well as part locator diagrams anddetailed schematic diagrams.

4.3 WHO SHOULD PERFORM REPAIRS

Only qualified service personnel should open the device housing, remove andreplace components, or make adjustments. If your medical facility does not havequalified service personnel, contact Mallinckrodt Technical Services.

4.4 REPLACEMENT LEVEL SUPPORTED

The replacement level supported for this product is to the printed circuit board(PCB) and major subassembly level. Once you isolate a suspected PCB, replacethe PCB with a known good PCB. Check to see that the trouble symptomdisappears and the device passes all performance tests. If the trouble symptompersists, swap the replacement PCB and the suspected malfunctioning PCB (theoriginal PCB that was installed when you started troubleshooting) and continuetroubleshooting as directed.

4.5 OBTAINING REPLACEMENT PARTS

Mallinckrodt Technical Services provides technical assistance information andreplacement parts. To obtain replacement parts, contact Mallinckrodt. Refer toparts by the part names and part numbers listed in Section 6, Spare Parts.

4.6 TROUBLESHOOTING GUIDE

Table 4-1 this section discusses potential symptoms, possible causes, and actionsfor their resolution. Should this troubleshooting guide fail to address thesymptoms evident in a particular N-20PA, please contact Mallinckrodt TechnicalServices or your local Mallinckrodt representative for assistance.

Troubleshooting

4-2

If the N-20PA does not perform as expected, the problem may be related to thefollowing:

• Incorrect sensor placement.

• Depending on concentration, indocyanine green, methylene blue, and otherintravascular dyes may affect the accuracy of a measurement.

• These instruments are calibrated to read oxygen saturation of functionalarterial hemoglobin (saturation of hemoglobin functionally capable oftransporting oxygen in the arteries). Significant levels of dysfunctionalhemoglobins such as carboxyhemoglobin or methemoglobin may affect theaccuracy of a measurement.

If the electronics or display functions, or both, require testing, refer to thePerformance Verification section.

Table 4-1 : Troubleshooting the N-20PA

Symptom Possible Cause RecommendedAction

No response to On/Offbutton.

1. Battery access door maynot be properly latched.

2. Batteries may bedischarged.

3. Batteries may beincorrectly installed.

4. Batteries may not bemaking proper electricalcontact.

5. Fuse F1 on the auxiliaryPCB may be open.

6. Dust may haveaccumulated under On/Offbutton causing loss ofelectrical contact.

1. Check access door andensure that it is properlylatched.

2. Exchange batteries for anew set.

3. Ensure that batteries areoriented according to thepolarity indicator.

4. Inspect battery contactsfor deformity; clean contactsto remove oxidization.

5. See Section 4.7.5,Replacing Fuses.

6. Clean contact points underOn/Off button (see Section5.2.1, N-20PA DisassemblyProcedures).

Pulse Search indicatorappears for more than5-10 seconds.

1. Sensor may be improperlypositioned.

2. Incorrect sensor may be inuse.

3. Perfusion may be too low.

4. Foreign material on the

1. Ensure that the sensor iscorrectly applied (see sensorDirections for Use).

2. See sensor Directions for Useto ensure that the patient’sweight and sensor applicationare correct. Test the sensor onanother person to verify properoperation.

3. Check patient status. Test theinstrument on someone else, ortry another type of sensor. TheN-20PA will not make ameasurement if perfusion isinadequate.

4. Clean the test area and ensure

Troubleshooting

4-3

sensor LEDs or photodetectormay be affecting performance.

5. Patient motion may beinterfering with the instrument’sability to find a pulse pattern.

6. Environmental motion maybe interfering with theinstrument’s ability to track apulse.

7. The sensor may be too tight,there may be excessiveillumination (for example, asurgical or bilirubin lamp ordirect sunlight), or the sensormay be placed on an extremitywith a blood pressure cuff,arterial catheter, or intravascularline; Mallinckrodt does notrecommend using a sensor onthe same limb as these threedevices.

8. The DB-9 sensor connectoron the N-20PA may be broken.

that nothing blocks the sensorsite.

5-7. If possible, ask the patientto remain still. Verify that thesensor is securely applied andreplace it if necessary, move itto a new site, or use a sensorthat tolerates patient movement,such as an appropriate adhesivesensor.

8. Replace the DB-9 connector.

Pulse Search indicatorappears after successfulmeasurements havebeen made.

1. Patient perfusion may betoo low.

2. Patient motion may beinterfering with theinstrument’s ability to find apulse pattern.

3. Environmental motionmay be interfering with theinstrument’s ability to track apulse.

4. The sensor may be tootight, there may be excessiveillumination (for example, asurgical or bilirubin lamp ordirect sunlight), or the sensormay be placed on anextremity with a bloodpressure cuff, arterialcatheter, or intravascularline; do not use the sensor onthe same limb as these threedevices.

1. Check patient status. Testthe instrument on someoneelse, or try another type ofsensor. The N-20PA will notmake a measurement ifperfusion is inadequate.

2-4.If possible, ask thepatient to remain still.Verify that the sensor issecurely applied and replaceit if necessary, move it to anew site, or use a sensor thattolerates patient movement,such as an appropriateadhesive.

Troubleshooting

4-4

Dashes (- - -) appear inthe display.

The sensor is not connectedto the instrument.

Check all sensorconnections; try substitutinganother sensor. Check allextension cables. If anextension cable is in use,remove it and plug the sensordirectly into the instrument.

Pr Err is displayedduring the POST.

The printer is not operational(however, the N-20PAcontinues to obtain patientmeasurements) due to paperjam or print head not in thehome position.

Check to see if the paper isjammed. Examine the printhead and ensure that it hasreturned to the homeposition. Turn the printer off,then on again.

Err followed by anumber appears on thedisplay.

See Section 4.7.8 for errorcodes.

Record the number that isdisplayed.

Time or date isincorrect.

The real-time clock (RTC)battery may be exhausted.

Replace the RTC battery (seeSection 4.7.4).

Resent the time and date (seeSection 4.7.3).

Printer fails to operate. Fuse F2 on the auxiliaryPCB may be open.

Batteries may be low.

1. See Section 4.7.5 forinformation about fuses.

2. Replace old batteries withfresh batteries.

Printer paper advancesbut instrument does notprint.

The thermal paper may beimproperly loaded;characters can be printed ononly one side of the thermalpaper roll.

Ensure that the thermal paperis properly loaded; if needed,remove the roll of printerpaper and reload the printerpaper.

Paper mechanism jams.

Note: If a printer paperjam is detected whenthe printer is turned on,Pr Err may appear onthe display.

Switch off the N-20PA. Thencheck to see if the print headis at the home position; if so,attempt to pull the paper outby pulling gently - - do notforce it.

If the print head is not at thehome position, and the papercannot be easily pulled outfrom the printer, then theprinter may need to bedisassembled to remove thepaper jam (see Sections 5.3,N-20PA DisassemblyProcedure, and 4.7.2,Loading/Clearing PrinterPaper).

4.7 Service Procedures

The following service procedures are most likely to be encountered by theservice technician. The PCB designation for a component appears inparentheses; for example, (BT1) or (U15).

Troubleshooting

4-5

4.7.1 Installing Batteries

The N-20PA operates on four 1.5-V alkaline “C” cell batteries. Do not useoff-the-shelf rechargeable batteries; this type of battery can cause the LowBattery indicator to be inaccurate. To install the batteries:

1. Remove the battery access door by pressing the battery compartment accessdoor latch.

2. Install four alkaline “C” cell batteries. Be sure to observe the polarityindicator sticker.

3. Replace the battery cover access door.

4.7.2 Loading/Clearing Printer Paper

The N-20PA uses a thermal paper that can show printed characters on one sideonly. Make sure that the paper roll is correctly installed; always refer to thegraphical instruction label found on the paper roll. To load the paper:

1. Press down and outward on the top of the paper compartment door to removeit.

2. Feed the paper into the paper compartment slot; refer to the graphic label fororientation.

3. Press and hold the ADV button until the end of the paper appears at the paperexit slot.

4. Replace the paper compartment door.

If the paper jams either during the loading process or during printing, proceed asfollows:

1. Remove both the paper door and the printer-head access cover.

2. Firmly grab and pull the paper roll backward—out and away from the printhead—and observe the print head access to determine whether or not thepaper escaped from the jammed position.

3. If paper remains jammed between the printer head and printer, press theADV button; the jammed paper may work its way out. If the paper remainsjammed, and the printer drive does not advance the paper, manually advancethe drive gear on the side of the printer to free the paper.

If these attempts fail to free the jammed paper, remove the printer from the unitto gain full access (see Section 5.3, N-20PA Disassembly Procedure).

4.7.3 Setting Date and Time

The following code letters and numbers appear in both Oxygen Saturation andPulse Rate display fields. The symbol “xx” represents information in theOxygen Saturation display field and “yy” represents information in the PulseRate display field.

1. To set the date and time: Remove any sensor from the instrument.

2. Switch on the N-20PA and allow the unit to run POST.

Troubleshooting

4-6

3. When dashes appear in the Oxygen Saturation and Pulse Rate displays, pressthe D/D (day/date) button once. At this point, the Oxygen Saturation displayshows “txx”, with “t” representing time; “xx” representing hours, and “yy”representing minutes. Note that “xx” (hours) is flashing.

4. Press the ADV (advance) button repeatedly until the correct hour isdisplayed.

5. Press the D/D button once. Note that “yy” (minutes) is now flashing.

6. Press the ADV button repeatedly until the correct minute is displayed.

7. Press the D/D button. At this point, the Oxygen Saturation display shows“dxx”, with “d” representing date; “xx” representing the day and “yy”representing the month. Note that “xx” (day) is flashing.

8. Press the ADV button repeatedly until the correct date is displayed.

9. Press the D/D button once. Note that “yy” (month) is flashing.

10. Press the ADV button repeatedly until the correct month is displayed.

11. Press the D/D button. At this point, the Oxygen Saturation display shows“Yxx,” with “Y” representing “year”. Note that “xx” (year number) isflashing.

12. Press the ADV button repeatedly until the correct year number is displayed.

13. Press the D/D button once. The N-20PA turns itself off immediately.

14. Verify that date and time are now correct by switching on the N-20PA andthen enabling the printer. After the N-20PA executes its POST, the printerprints the header with the correct date and time.

Note: The parenthetic line description is not printed. Button presses areignored whenever the printer is printing.

Note: If in the D/D mode and there is no user interaction (no buttons are beingpressed) for 60 seconds, the N-20PA turns off and any changes made arenot saved.

4.7.4 Replacing the Real-Time Clock (RTC) Battery

The socket for the RTC battery (BT1) is located on the auxiliary PCB. Typicallife of the clock battery is 5 years.

Caution: After replacing an RTC battery, switch the instrument on, thenimmediately switch it off; this action will prevent possible damage to theRTC voltage circuit.

To replace the real-time clock/battery:

1. Disassemble the N-20PA (see Section 4.3, Disassembly Guide).

2. Using a thin flat-head screwdriver, gently pry the RTC battery from itssocket.

3. Insert a new battery into the socket, observing the polarity indication(socket’s clip and battery’s flat side are positive).

4. Reassemble the unit.

5. Switch on the instrument, then immediately switch it off (the RTC voltagecircuit requires this step to prevent possible damage to the unit). Theinstrument is now ready for normal operation.

Troubleshooting

4-7

6. Reset the clock (see paragraph 4.7.3, Setting Date and Time).

4.7.5 Replacing Fuses

Two fuses (F1 and F2) are located on the auxiliary PCB. Fuse F1 may open toprotect the CPU and its associated components from damage if the power supplymalfunctions. Fuse F2 may open to protect the printer from damage due toexcessive voltage if the printer head jams or if it has been physically damaged.Refer to the auxiliary PCB schematic for the locations of F1 and F2.

4.7.6 Replacing the DB-9 Connector

To replace the DB-9 connector:

1. Disassemble the N-20PA (see Section 5); the connector is on the main PCB.

3. Using a low-power soldering iron, unsolder the connector from the PCB andremove it.

Note: Save all Teflon tubing, ferrite blocks, and insulating materials for thereplacement connector.

3. Install ferrite blocks between the plastic lead spacer on the connector and thePCB.

4. Insulate connector pin numbers 2, 3, and 5 with Teflon tubing, and insertinside ferrite block.

5. Add insulating material between each end of ferrite block and the PCB, andsecure with Loctite glue.

6. Solder new connector to the PCB and visually check the PCB for stray dropsof solder before reassembling.

7. Switch on the N-20PA and test the connector with a patient sensor.

4.7.7 Adjusting Printer Darkness

Caution: Adjust the printer darkness setting until the lightest legible printis visible. Setting the print darker than this could reduce printer-head life.

Although the N-20PA is designed to automatically compensate for conditionsthat might influence the quality of the printout, the user may want to adjust theprint darkness. The normal darkness setting is set at the factory; this settingmaximizes both readability and printer head life.

Note: This procedure cannot be performed after a valid pulse is receivedfollowing power-on. Hence, perform this procedure with no sensorattached to the monitor.

To adjust the printer darkness:

1. Switch on the N-20PA.

Troubleshooting

4-8

2. Simultaneously press and hold the ADV and printer ON buttons for 4seconds. If these buttons are not pressed at the same time, two audible beepswill sound and the N-20PA either advances the paper or turns on (or off) theprinter, depending on which button-press is first sensed. If the buttons arepressed at the same time, a single audible beep will sound, Pr SEt isdisplayed, and the printer prints one of the following 6 lines:

PRINTING LIGHTER (10% lighter than normal)

PRINTING LIGHT (5% lighter than normal)

PRINTING NORMAL (normal darkness)

PRINTING DARK (5% darker than normal)

PRINTING DARKER (10% darker than normal)

PRINTING DARKEST (15% darker than normal)

Note: The parenthetic line description is not printed. Button presses areignored whenever the printer is printing.

1. Press the ADV button to change the darkness setting. The printer prints aline with each button press, and the setting increments from lighter todarkest and then wraps back to lighter.

2. Allow the N-20PA to switch off (about 30 seconds). The last printerdarkness setting is remembered when the N-20PA is switched back on.Test this by repeating the procedure and skipping step 3.

4.7.8 Error Codes

If a failure is detected during the Power-On Self-Test or during any performancetest, the error message (Err) appears in the Oxygen Saturation display and a3-digit error code number appears in the Pulse Rate display.

If an error message appears, record the error code number. Match the number tothe description in the following table, and contact Mallinckrodt’s TechnicalServices Department or your local Mallinckrodt representative for assistance.The first digit of the error code is the category.

Internal tests are performed in the order listed in the table. The first errorcondition encountered is the one displayed.

Troubleshooting

4-9

Category 1 — Microprocessor Errors

Errors in the CPU (main PCB). Likely action is replacement of the CPU.

101

102

103

104

105

106–109

110

111

112

113,114

115–117

118

119

120

121

122

123

124

125

126–129

Error in internal RAM register test

Error in zero register test

Error in register contents clearing test

Error in register contents increment test

Error in register contents decrement test

Errors in logical operations test

Error in exchange test

Error in timer tests

Error in window select register test

Errors in stack manipulation test

Errors in CPU flags test

Error in interrupt pending register test

Error in program counter test

Error in CPU serial port test

Error in pulse width modulation register test

Error in A/D register test

Error in addressing modes test

Error in high-speed input register test

Error in content addressable memory test

Errors in arithmetic operations test

Category 2 — RAM Memory Errors

Errors in RAM memory (main PCB). Likely action is replacement of the mainPCB.

201-203 Errors in external RAM test

Category 3 — PROM Errors

Errors in PROM memory (main PCB). Likely action is replacement of thePROM.

301 Error in PROM test

Category 4 — I/O Port Errors

Errors in the CPU internal I/O port (main PCB). Likely action is replacement ofeither the CPU or the main PCB.

401-409 Errors in I/O port test

Category 5 — Reserved

Troubleshooting

4-10

Category 6 — Clock Errors

Failure of the real-time clock (auxiliary PCB), or timing differences between theCPU clock and the real-time clock. Likely action is replacement of the main orauxiliary PCB.

601

602, 603

Failure of real-time clock

Errors in real-time clock

Category 7 — Watchdog-Timer Errors

Error in the watchdog-timer circuit of the CPU (main PCB). Likely action isreplacement of the CPU.

701, 702 Errors in watchdog-timer

Category 8 — Printer Errors

Error in the printer. If a printer error condition occurs, the display reads Pr Err.See the Troubleshooting section for further information on this error.

5-1

SECTION 5: DISASSEMBLY GUIDE5.1 Introduction5.2 Beginning Disassembly5.3 N-20PA Disassembly Procedure

5.1 INTRODUCTION

The device can be disassembled down to all major component parts, including:

• PCBs

• batteries

• cables

• chassis enclosures

Tools required:

• small, Philips-head screwdriver

• small flat-head screwdriver

• needle-nose pliers

• low-power soldering iron

WARNING: Before attempting to open or disassemble the device, turn itoff.

Caution: Observe ESD (electrostatic discharge) precautions when workingwithin the unit.

5.2 BEGINNING DISASSEMBLY

20

34

19

21

Figure 5-1: Sensor Lock, Printer, Paper, and Battery Access Doors

Figure 5-1 shows the how to start the N-20PA disassembly.

Section 5: Disassembly Guide

5-2

1. Remove the battery door (19) and batteries.

2. Remove the sensor lock (34) by lightly pressing in on its ears and pulling outfrom the sensor shroud.

3. Remove the paper door (20), paper roll, and the printer door (21).

5.2.1 Removing the Covers

16

18

27

26

15

31

30

Figure 5-2: N-20PA Covers with the PCB and Display Assembly

Figure 5-2 shows how to remove the N-20PA cover and display assembly.

1. Remove screw cap (30) and loosen the captive screw (31) that secures therear battery cover (15).


5-3

2. Separate the front cover (16) from the rear battery cover by wedging a thinflat-head screw driver between the covers at the base of the instrument andslowly prying them apart.

Note: The covers are hinged at the top end in a different way; do not attempt toseparate the covers using this technique at the top of the instrument.Once the covers are separated at the bottom end, lift away the bottomend of the front cover first, allowing the tabs at the top end to act as ahinge.

5.2.2 Removing the PCBs and Display Assembly

18

Tab #4

Tab #1

Tab #2

Tab #3

Detail A

Detail B

26

13

12

11

27

6Flex #1

Flex #3Flex #2

5

Figure 5-3: Main, Auxiliary, and Display PCB Assembly

Figure 5-3 shows how to remove the PCB assemblies.

1. Remove the On/Off button (6) from the main PCB.

2. Remove the entire PCB/Taliq display assembly from the rear battery coverby tilting opposite the battery-check button (5).

3. Release connectors (11, 12, and 13) on the auxiliary PCB (26) and removethe three flex display circuits.

4. Separate the auxiliary PCB from the main PCB (27) by pulling the PCBheaders apart at the base.

5. Remove the display assembly (18) from the main PCB by unsoldering thefour tabs that are physically bent around the main PCB. These tabs are bentto ensure contact with the ground plane of the main PCB.

6. Using long-nose pliers, remove the metal shroud by untwisting the four tabs(see Detail A and B).


5-4

5.3 DISASSEMBLYING THE PRINTER/FLEX CIRCUIT ASSEMBLY

24

28

37

7

29

32

4

Figure 5-4: Printer and Flex Circuit Assembly

Figure 5-4 shows how to disassemble the printer and flex circuitry.

1. Remove the printer button stiffener (37).

2. Disconnect the two flex-circuit headers of the printer (29) from theconnectors on the printer flex circuit (28) by slowly pulling them outwardfrom side to side at alternating ends of the connectors.

3. Remove the printer button strip (7) from the printer flex-circuit.

4. Remove the printer flex-circuit insulator (24).

5. Remove the printer hold-down bracket (4) from the back cover by removingthe Phillips screw (32).

6. Press the printer hold-down bracket into the back cover and remove theprinter.

6-1

SECTION 6: SPARE PARTS6.1 Introduction6.2 Spare Parts List

6.1 INTRODUCTION

Spare parts, along with corresponding part numbers, are shown below. To orderreplacement parts, contact Mallinckrodt’s Technical Services Department andorder by part number.

6.2 SPARE PARTS LIST

Item Designator Description P/N

1 SW1 Battery switch (auxiliary PCB) 630106

2 BT1 Battery holder (auxiliary PCB) 901582

3 BT1 Battery, lithium (auxiliary PCB) 640112

4 Bracket, printer, hold-down 023133

5 Button, battery-check 023301

6 S2 Button, measure 022948

Button, measure (European version) 026386

7 Buttons, printer, strip 022947

Buttons, printer, strip (European version) 026387

8 L1, L2 Coil, 120 µH SMT (auxiliary PCB) 691238

9 Connector shield, DB-9 023467

10 P1 Connector, DB-9 463103

11 JP17, JP18 Connector, pin header 10x2, low profile(auxiliary PCB)

491244

12 JP5 Connector, ZIF, flex, 7-pin (auxiliary PCB) 491242

13 JP9 Connector, ZIF, flex, 22-pin (auxiliary PCB) 491250

14 JP2, JP3 Connector, ZIF, flex, 32-pin (auxiliary PCB) 491243

15 Cover, battery, rear (non-printer model) 022929

Cover, battery, rear (printer model) 026339

16 Cover, front, with gasket assembly 022921

17 D8 Diode, photo, 8440 (main PCB) 591017

18 Display, Taliq, analog shield assembly 024466

Display, Taliq, analog shield assembly(European version)

026765

19 Door, battery 022924

20 Door, paper. 022938

Spare Parts

6-2


21 Door, printer 026338

22 F2 Fuse, micro, 1 amp (auxiliary PCB) 691236

23 F1 Fuse, micro, 1.5 amp (auxiliary PCB) 691239

24 Insulator, printer 026139


25 Nut, keps, SS, 4-40 851101

26 PCB, auxiliary 024472

27 PCB, main 024468

28 Printer flex circuit 024464

29 Printer 024462

30 Screw cap 023451

31 Screw, captive 891324

32 Screw, Phillips, 4-40 x 1/4 801025

33 Screw, plastite 871031

34 Sensor lock 022943

35 Sensor shroud 022944

36 Spacer 023452

37 Stiffener, printer button 023131

38 Tape, foam (.88” x .38”) 023300

39 BZ1 Transducer, audio, piezo ceramic 691230

7-1

SECTION 7: PACKING FOR SHIPMENT7.1 General Instructions7.2 Repacking in Original Carton7.3 Repacking in a Different Carton

Should you need to ship the N-20PA monitor for any reason, follow theinstructions in this section.

7.1 GENERAL INSTRUCTIONS

Pack the monitor carefully. Failure to follow the instructions in this section mayresult in loss or damage not covered by the Mallinckrodt warranty. If theoriginal shipping carton is not available, use another suitable carton or callMallinckrodt Technical Services to obtain a shipping carton.

Prior to shipping the device, contact Mallinckrodt Technical Services for areturned goods authorization (RGA) number. Mark the shipping carton and anyshipping forms with the RGA number.

7.2 REPACKING IN ORIGINAL CARTON

If available, use the original carton and packing materials. Pack the monitor asfollows:

1. Place the monitor and, if necessary, accessory items in original packaging.

2. Place in shipping carton and seal carton with packaging tape.

3. Label carton with shipping address, return address, and RGA number.

7.3 REPACKING IN A DIFFERENT CARTON

If the original carton is not available:

1. Place the monitor in plastic bag.

2. Locate a corrugated cardboard shipping carton with at least 200 pounds persquare inch (psi) bursting strength.

3. Fill the bottom of the carton with at least two inches of packing material.

4. Place the bagged unit on the layer of packing material and fill the boxcompletely with packing material.

5. Seal the carton with packing tape.

6. Label carton with shipping address, return address, and RGA number.

8-1

SECTION 8: SPECIFICATIONS8.1 Performance8.2 Alarms8.3 Electrical8.4 Environmental8.5 Physical

8.1 PERFORMANCE

8.1.1 Range

Saturation

0–100%

Pulse Rate20–250 beats per minute (bpm)

8.1.2 Accuracy

SpO21

Adults 70–100% ± 2 digits2

0–69% unspecified

Neonates 70–95% ± 2 digits2

0–69% unspecified

Pulse rate20–250 bpm ± 3 bpm2

8.2 ALARMS

8.2.1 Alarm Limit Range

Saturation20–100%

Pulse Rate30–250 bpm

1 The reference for accuracy testing is an N-200 oximeter and D-25 sensors that have been validated inhuman blood studies against an Instrumentation Laboratories CO-Oximeter. Adult accuracy specificationis based on testing with D-25 sensors; neonatal accuracy specification is based on testing with N-25sensors. For specifications with other NELLCOR sensors, see the sensor Directions for Use.2 This variation equals one standard deviation (SD). Plus or minus one SD encompasses 68% of thepopulation.

Section 8: Specifications

8-2

8.2.2 Factory Default Alarm Settings

Adult Neonate

SpO2 Upper Limit: 100% 95%

SpO2 Lower Limit: 85% 80%

PR Upper Limit: 170 bpm 190 bpm

PR Lower Limit: 40 bpm 90 bpm

8.3 ELECTRICAL

8.3.1 Battery

TypeFour alkaline “C” size batteries

Battery CapacityTypically 32 hours with four alkaline “C” size batteries1

8.3.2 Instrument

Power Requirements4–6 V, supplied by battery only

Patient IsolationNo electrical connection to patient (inherently isolated)

8.4 ENVIRONMENTAL

8.4.1 Operating Temperature

Instrument0 to 40°C

SensorWithin physiologic range for specified accuracy

8.4.2 Storage Temperature

–20 to 50°C

8.4.3 Humidity

Any humidity/temperature combination without condensation

8.4.4 Altitude

0–6200 m (0–20,000 ft)

1 Not all brands of off-the-shelf alkaline batteries provide the same battery life.

Section 7: Specifications

8-3

8.5 PHYSICAL

8.5.1 Weight (with batteries installed)

0.6 kg (1.3 lb)

8.5.2 Size

19.0 cm high × 7.6 cm wide × 6.35 cm deep(7.5 in. × 3.0 in. × 2.5 in.)

9-1

SECTION 9: TECHNICAL SUPPLEMENT

9-1 Introduction

9-2 Functional Overview

9-3 Definition of Terms

9-4 Overall Block Diagram

9-5 SpO2 Analog Circuitry

9-6 Digital Circuitry

9-7 Circuitry Illustrations

9.1 INTRODUCTION

This Technical Supplement provides the reader with a discussion of the N-20PAcircuits. This discussion is supported with applicable illustrations, includinggraphics that have been placed on reverse-fold pages so they can be easilyreferenced while reading the text. The foldout graphics and schematics arelocated at the end of this supplement.

9.2 FUNCTIONAL OVERVIEW

The N-20PA consists of three main components:

• The N-20PA main printed circuit board (PCB)

• The N-20PA auxiliary PCB

• The N-20PA flex circuit

The relationship between these components and their interconnection isillustrated in the overall block diagram (Figure 9-1). The main componentcircuitry has been divided into the following subsections:

SpO2 analogMicroprocessorMemoryDisplay controlSensors: temperature ambient light battery voltage

PROM Measurebutton

Auxiliary PCB

Power supplyPrinter interfaceDisplay controlAudio beeper

Real- timeclock

Checkbatterybutton

Batteries

6 VDC

Patientsensor

Main PCB

20-Pin headers

Displaybacklight

Printerflex circuit Printer

Flexconnectors

Figure 9-1: Overall Block Diagram

Technical Supplement

9-2

• SpO2 Analog Block Diagram (Figure 9-2) — Analog circuitry has highsignal sensitivity and reduced susceptibility to noise. Its design allows for awide range of input signal levels and a broad range of pulsatile modulation.The SpO2 analog circuit consists of four subsections:

1. Sensor output/LED control, where the CPU controls the gain of both LEDsso that signals received at the input amplifier are in its acceptable dynamicrange

2. Input signal conditioning, where sensor output current is converted tovoltage

3. Signal gain, where the separated LED signals are amplified so their currentlevels are within the A/D converter’s acceptable range

Zeroing

and

Current toVoltage

Conversion

Inve

rter DMUX

Variable Gainand Filter


OffsetSubtraction

OffsetSubtraction


CPU

LED Drive

Sensor

Input SignalConditioning Signal Gain AC Ranging

SAMPIR

SAMPRED

PWM1

AC + DC

/ZERO

PWM0

REDAC

PWM2

PWM0

IRAC

AC + DC

/ZERO

IR/RED

OFF/ON

LED DIS

PWM0, PMW1, PWM2

Output

IR

RED

RSENS

IR

RED


Figure 9-2: SpO2 Analog Block Diagram

4. AC ranging, where DC offset is eliminated from each LED signal

• Hardware Block Diagram (Figure 9-3) — This diagram shows the N-20PAhardware and circuits, which include: the CPU and system memory, thepower supply and power control circuitry, user controls, display and ambientlight sensors, audio output, thermal printer and ambient temperature sensor,and the real-time clock.

• Power Supply Block Diagram (Figure 9-4) — Power supply circuitry islocated on the auxiliary PCB and consists of four subsections:

1. Four “C” size batteries that provide 4-6 VDC

2. Power control circuitry that senses a press of the On/Off button and switchespower on

3. Power shutoff circuit that controls power to all circuits except the powercontrol circuit

4. Power supply circuits include: a regulated power supply at 5 VDC,unregulated power supplies of -5 VDC, 10 VDC, and 12 VDC, and ahigh-voltage power supply of 70 VDC


9-3

AnalogReferenceVoltage

AmbientLight

BatteryVoltage

AmbientTemperature

BatteryPower

PowerControl

SerialInterface

SpO2AnalogSection

PatientSensor

AddressDecoding

AddressDemultiplexing

StandardUser

Supply

PowerSupply

CPUMemory

InputPort

OutputPort

BatteryType

LithiumBattery

Real TimeClock and

Non-VolatileMemory

AudioOutput

DisplayControl

PrinterInterface

UserDisplay Optional Printer

Flex Circuit withUser Controls

CPU

Analog

Control

Analog

PowerOff

PowerControl

Pow

er O

n

Add

ress

AD BusControl

AD Bus

Enables

Digital I/O

Digital I/O

Input Port

Output Port

UserControls

Pow

er C

ontr

ol

External to Board

BUSSES

SIGNALS

Figure 9-3: N-20PA Hardware Block Diagram


9-4

Powershutoffcircuits(fuse;

EMI protect;ESD protect)AUX PCB

AUX PCB

Disposablebatteries

Powercontrolcircuits

On/Offbutton

4–6 VDCDisplay drivers

Microprocessor

Display backlight

+5 VDC

+70 VDCPowersupplycircuits AUX PCB

Main PCB

SpO2 Analogsection

(main board)

–5 VDC +10VDC

+12 VDC

Figure 9-4: Power Supply Block Diagram

• Display Control Block Diagram (Figure 9-5) — The N-20PA display iscontrolled by the display control circuitry. A sensor is used to measureambient light. During low-light conditions, the display backlight, anelectroluminescent device, is automatically switched on.

Main PCB

Microprocessor

Main PCB

Controlconditioning

circuit(generates

timingsignals)

AUX PCB

Display driver(1)

Display driver(2)

70 volts

AUX PCB

High voltagecontrol circuit

(enables+70 VDCto display)

Display

Displaybacklight

Figure 9-5: Display Control Block Diagram

• Printer Control Block Diagram (Figure 9-6) —Printer circuitry is dividedinto two subsections: the printer interface and the printer flex circuit.


9-5

Printerinterface

Printer flex

circuitPCB

Printer

Main PCB

User push buttons

AUX PCB

Microprocessor

On ADV D/D

Figure 9-6: Printer Control Block Diagram

9.3 DEFINITION OF TERMS

Analog to Digital (A/D) converter. The CPU has a 10-bit A/D converter onboard. Up to eight different analog inputs can be provided to the A/D converterfor measurement.

Central Processing Unit (CPU). An Intel 80C196KC 16-bit microcontroller.The CPU sends and receives control signals to the SpO2 analog section, display,and optional printer.

Content Addressable Memory (CAM). The CPU controls the HSO lines withthe CAM. CAM is controlled by software and programmed with eventsscheduled relative to one of two internal timers.

High Speed Outputs (HSO). The 6 HSO lines control most of the timing of theLED signal pulse and the demodulation of the received signal.

Input and Output (I/O). Digital lines that are used by the CPU to read in dataand output data.

Light Emitting Diodes (LEDs). Two LEDs are used in Nellcor oximetrysensors. Light is transmitted through body tissue and received by aphotodetector circuit that converts it to photocurrent. The two wavelengths,which are used for calculation of pulse rate and oxygen saturation in blood, aretransmitted at the following frequencies:

• infrared (IR) light at approximately 915 microns

• red light at approximately 660 microns

Pulse Width Modulation (PWM). The three 8-bit PWM outputs can besoftware controlled; their duty cycle can be changed from 0-255/256 of the totalpulse duration. PWM frequency is the crystal frequency of the CPU, which is 10MHz divided by 1024. The PWMs control the gains within the analog circuit.

RCal. Sensor RCal value is a resistance value specific to an individual sensor.This value is used by the software during oxygen saturation computations tomaximize accuracy.

Real-Time Clock (RTC). The RTC is used with the optional printer to tracktime and date for printouts.


9-6

9.4 OVERALL BLOCK DIAGRAM

Exclusive of covers, buttons, and external connectors, the N-20PA consists ofthree main components: the main PCB, the auxiliary PCB, and the displayassembly and analog shield.

• Main PCB — Contains the SpO2 analog circuitry; the CPU; supportmemory circuits; sensor circuits for ambient light, temperature, and batteryvoltage; the check battery circuit; a serial data port; and some display controlcircuits.

• Auxiliary PCB — Contains the power supply circuitry; the display drivercircuits; the real-time clock; the interface circuitry for the printer flex circuitboard (which is not used unless a printer is present); and audio outputhardware.

• Display and Analog Shield Assembly — This assembly connects to themain PCB by flex circuits. A metal shield shrouds the SpO2 analog circuitson the main PCB to protect them from EMI. An integratedelectroluminescent backlight illuminates the display under low lightconditions.

The N-20PA has an additional printer control board (printer flex circuit), andprinter hardware. Figure 9-1 shows the relationship of these components.

9.5 SPO2 ANALOG CIRCUITRY

This subsection describes the SpO2 analog hardware. The analog circuitry hashigh signal sensitivity and reduced susceptibility to noise. Its design allows for awide range of input signal levels and a broad range of pulsatile modulation. TheSpO2 analog block diagram (Figure 9-2) consists of four subsections:

• Sensor output/LED control — The CPU controls the drive level of bothLEDs so that signals received at the input amplifier are within an acceptabledynamic range. Signal channel gain may also need to be increased. TheCPU uses PWM lines to control the LED current level or to amplify thesignal channel.

• Input conditioning — Sensor detector current is converted to voltage. Ademodulation circuit minimizes the effects of other light sources and strayfrequency inputs. Because the infrared (IR) and red signals are at differentcurrent levels, the two LED signals are demultiplexed and separatelyamplified, so they can be compared with each other. Two circuits handle thedemultiplexing by alternately selecting LED signals using switches. Filtersthen remove noise and smooth the signals before sending them to theamplifiers.

• Signal gain —The separated LED signals are amplified so that their currentlevels are within the A/D converter’s acceptable range. The signals arefiltered to improve the signal-to-noise ratio, and clamped to a referencevoltage.

• AC ranging —DC offset is eliminated from each LED signal. An analogswitch sets the mean signal value to the mean of the A/D converter range,and the AC modulation is superimposed on that DC level. Then, each ACsignal is amplified and filtered to eliminate residual effects of the PWMmodulations. Finally, these two signals are input to the CPU A/D converter.


9-7

The relationship of these subsections is shown in Figure 9-7.

Patientsensor

LEDs

Input signalconditioningphotocurrent

to voltageconversion

demutiplexedto 2 channels

Main PCB

Signal gain

variable gain,filtered foreach LEDchannel

Main PCB

AC Ranging

offsetsubstraction;

additional gainand filtering

Main PCB

Microprocessor

Main PCB

To digital section

Control

Main PCB

LED drivers(red & IR)

Figure 9-7: SpO2 Analog Circuitry Block Diagram

9.5.1 Sensor Output/LED Control

The SpO2 analog circuitry provides control of the red and IR LEDs such that thereceived signals are within the dynamic range of the input amplifier. Becauseexcessive current to the LEDs will induce changes in their spectral output, it issometimes necessary to increase the received signal channel gain. To that point,the CPU controls both the current to the LEDs, and the amplification in thesignal channel.

At initialization of transmission, intensity level of the LEDs is based on previousrunning conditions; and, the transmission intensity is adjusted until the receivedsignals match the range of the A/D converter. If the LEDs reach maximumoutput without the necessary signal strength, the PWMs will increase the channelgain. The PWM lines will select either a change in the LED current or signalgain, but will not do both simultaneously.

The LED circuit switches between red and IR transmission and disables both fora time between transmissions in order to provide a no-transmission reference.To prevent excessive heat buildup and prolong battery life, each LED is on foronly a small portion of the duty cycle. Also, the frequency of switching is wellabove that of motion artifact and not a harmonic of known AC transmissions.The LED switching frequency is 1.485 kHz. The IR transmission alone, and thered transmission alone will each be on for about one-fifth of the duty cycle; thiscycle is controlled by the HSOs of the CPU.

9.5.1.1 LED Drive Circuit

The LED drive circuit is illustrated in Figure 9-8, at the end of section 9.


9-8

The IR and red LEDs are separately controlled with their drives currentsmultiplexed over two shared wires. Current to the IR LED is in the range of4.3-50.0 mA; and, current to the red LED is in the range of 6.5-75.0 mA.Currents are limited to less than 100 mA for two reasons: (1) slight excesscurrent can potentially change the emission characteristics of the LEDs, and (2)large excess current could create excessive heat at the sensor site.

The IR/red LED transmission signal (HSO1 of the CPU) is fed into the selectinputs of the triple single-pole-double-throw (SPDT) analog multiplexing switchU10, causing either the IR or the red LED transmission to be enabled.

PWM1, which is filtered by the network of R44, C37, R52, and C38, is input tothe LED drive circuit switch U10, and controls the magnitude of the IR LEDcurrent supply.

PWM2, which is filtered by the network of R43, C36, R53, and C39, is alsoinput to U10, and controls the red LED current magnitude.

Two NPN transistors (Q1 and Q2) act as current regulators for the IR and redLED return lines. Two PNP transistors (Q3 and Q4) act as switches between theIR and red LED output lines. Transistor Q5 acts as an LED drive current limiter;it clamps output of the current regulator circuit to the required level. If anyresistor in the LED drive circuit fails, current to the LED will still be limited to asafe level.

The RSENS line senses the RCal value and enables the CPU to make the propercalculations based on the type of sensor being used.

9.5.2 Input Conditioning

Input to the SpO2 analog circuit is the current output of the sensor photodiode.In order to condition the signal current, it is necessary to convert the current tovoltage.

A synchronous demodulation circuit is used to reduce the effects of other lightsources and stray frequency inputs to the system. Because the IR and red signalsare absorbed differently by body tissue, their received signal intensities are atdifferent levels. Therefore, the IR and red signals must be demodulated and thenamplified separately in order to compare them to each other. Demultiplexing isaccomplished by means of two circuits that alternately select the IR and redsignals. Selection of the circuits is controlled by two switches that arecoordinated with the IR and red transmissions. A filter with a large timeconstant follows to smooth the signal and remove noise before amplification.

9.5.1.2 Differential Synchronous Demodulation Circuit

The differential synchronous demodulation circuit is illustrated in Figure 9-9.

Before the current from the photodetector is converted to voltage, C40 and R17filter any high frequency noise. The op-amp U1A is used in parallel with thecurrent-to-voltage converter U1D to cancel any DC voltage, effectively ACcoupling the output of U1D. The average value of the SpO2 analog referencevoltage (VREF) of U1D, 5 V, is measured at test point 49.


9-9

15.8K

R56

LT1013

U9B

5 4

3PHOTOI

VREF

40.2KR57

L1

TP44SENSORINPUT

DB9F

P1

1 6 2 7 3 8 4 9 5

LF444

U1A

11

4

1 2

3182K

R1

390PFC40

3.32KR58

3.32KR17

1M

R2

VREF

LF444

U1D

14 13

12

TP49

.047UFC22

.047UFC59

511KR157

280KR19

VREF

18PF

C1

-5V

LTC201U6B

14 15

61

LTC201U6A

3 2

1

+12V

.1%88.7K

R159

LT1097

U35

4 81

57

6 3

2

-5V

+12V

LTC201U6D

7 6

8

.1%88.7KR158

2.0KR63

51.1K

R160

1M

R23

VREF

TP79

TP78

LTC201U6C 10

9 11

VREF

3.32K

R27

3.32K

R26

.47UFC25

.47UFC24

82.5K

VREF

SAMPREDSAMPIROFF/ON

RED

IR

Figure 9-9: Differential Synchronous Demodulation Circuit

The same line that controls the on/off pulsing of the LEDs controls U6D, asingle-pole-single-throw (SPST) analog switch. When either of the LEDs is on(the line is low and the switch is closed), U35 is used as a noninvertingamplifier. When the LEDs are both off, U35 is used as an inverting amplifier.The signal at the output of amplifier U35 is then demultiplexed.

The CPU HSO lines SAMPRED and SAMPIR, which are both active low,control SPST analog switches U6A and U6B respectively. Switch U6A is closedto sample the red signal; switch U6B is closed to sample the IR signal. Thesampling rate for both switches is 10 kHz. Switching is coordinated with theLED transmission so that the IR and red signals are each sampled twice percycle; that is, once when the LED is off (signal inverted), and once when theLED is on (signal not inverted). The filtering circuit that follows has a long timeconstant, thereby acting as an averaging circuit.

A simplified N-20PA HSO timing diagram is illustrated in Figure 9-10, at theend of Section 9.


9-10

If the instantaneous average photocurrent (DC offset) is excessive and U1Dcannot bring it to VREF, the PHOTOI line to the CPU (HSI0) is activated. Thisaction is an indication of excess ambient light into the photosensor, or theoccurrence of excess noise in the input circuit. It also serves as a warning to theinstrument that the sensor signal may be contaminated and causes the software tosend an error message. After about 3 seconds of continuous photocurrent signal,pulse search annunciation will begin. After about 10 seconds of continuousphotocurrent signal, zeros will be displayed.

9.5.3 Signal Gain

The separated IR and red signals are amplified so that their DC values are withinthe range of the A/D converter. Because the received IR and red signals aretypically at different current levels, the signal gain circuits provide independentamplification for each signal as needed. The gain in these circuits is adjusted bymeans of the PWM lines.

After the IR and red signals are amplified, they are filtered to improve thesignal-to-noise ratio and clamped to a reference voltage to prevent the combinedAC and DC signals from exceeding an acceptable input voltage from the A/Dconverter.

9.5.3.1 Variable Gain Circuit

The variable gain circuits are illustrated in Figure 9-11.

3.32K

R26

.47UFC24

1NF

C33

1NFC34

82.5K

R25

82.5K

R24

VREF 2N3906

Q7 220PF

C127

220PFC126

2N3906

Q6

TP52

TP51LF444

U1C8

10

9

LF444

U1B

75

6

VREF

VREF

-5V

.1UF

C35

.1UF

C122VREF

47.5K

R39

OFF/ON

4053

U2

7VEE

8VSS

16VDD

4Z

15Y

14X

9C

10B

11A

6INH

3Z1

5Z0

1Y1

2Y0

13X1

12X0

VCC PWM1IR LED/AV

To LED controlPWM2

RED

IR

IR

RED

Figure 9-11: Variable Gain Circuit


9-11

The two variable gain circuits are functionally equivalent. The gain of eachcircuit is contingent upon the signals received level and is controlled to bringeach signal to approximately 3.5 V. Each circuit uses an amplifier and oneswitch in the triple SPDT analog multiplexing unit U2.

The gain in each of the circuits is accomplished by means of a feedback loop,which includes one of the SPDT switches in U2. The PWMs control whether thefeedback loop is connected to ground or to the amplifier output. The feedback isthen averaged by C33/R25 (red), and C34/R24 (IR). The higher the value ofPWM2, the greater the IR gain; the higher the value of PWM1, the greater thered gain.

9.5.3.2 Filtering Circuit

The filtering circuits are illustrated in Figure 9-12.

1N914

CR4

1N914

CR2

VREF

.068UF

C20

OP490SO

U4B

76

5

-5V

1N914CR3

100K

R13

100K

R12

R11

R10

100K

R9

100K

R8

100K

R7

100K

R6

.068UFC17

.068UF

C14

.068UFC15

.12UFC19

C18

.12UF

C16

OP490SO

U4D

1615

14

U4A

31

4

1

+12V

1N914

CR1

U4C

10 11

12

VREF

.12UF

C13

TP90

TP82

TP89

TP81

100K

100K.12UF

OP490SO

2

3

OP490SO

IRDC

REDDC

RED

IR

Figure 9-12: Filtering Circuit

These circuits consist of two cascaded second-order filters with a breakfrequency of 10 Hz. Pairs of diodes (D1/D3 and D2/D4) that are locatedbetween VREF and ground at the positive inputs of the second amplifiers,maintain the voltage output within the range of the A/D converter.


9-12

9.5.4 AC Ranging

In order to achieve a specified level of oxygen saturation measurement and tostill use a standard-type combined CPU and A/D converter, the DC offset issubtracted from each signal. Because the DC portion of the signal can be on theorder of one thousand times the AC modulation, 16 bits of A/D conversionwould otherwise be required to accurately compare the IR and red modulationsbetween the combined AC and DC signals. The DC offsets are subtracted byusing an analog switch to set the mean signal value to the mean of the range ofthe A/D converter whenever necessary. The AC modulation is thensuperimposed upon that DC level. This is known as AC ranging.

Each AC signal is subsequently amplified such that its peak-to-peak values spanone-fifth of the range of the A/D converter. The amplified AC signals are thenfiltered to remove the residual effects of the PWM modulations and finally, areinput to the CPU. The combined AC and DC signals for both IR and red signalsare separately input to the A/D converter.

9.5.4.1 Offset Subtraction Circuits

The AC variable gain control circuit is illustrated in Figure 9-13, at the end ofthis section.

Voltage dividers R22 and R41 (red), and R31 and R5 (IR), which are locatedbetween VREF and ground, establish a baseline voltage of 2.75 V at the input ofthe unity gain amplifiers U7C (red) and U7D (IR).

Whenever SPST analog switches U11A and U11D are closed by HSO0 (activelow), the DC portions of the IR and red signals create a charge, which is storedon C29 and C89, respectively. These capacitors hold this charge even after theswitches are opened and the resulting voltage is subtracted from the combinedsignal—leaving only the AC modulation output. This AC signal issuperimposed on the baseline voltage output by U7C and U7D. The IRDC andREDDC are then filtered and input to the CPU, and can be measured at TP58and TP54, respectively.

9.5.4.1 AC Variable Gain Control Circuits

The AC variable gain control circuit is illustrated in Figure 9-13, at the end ofsection 9.

The AC modulations are amplified by U7A (red) and U7B (IR) andsuperimposed on the baseline voltages present at the output of U7D (IR) andU7C (red). The amplification is handled by means of the SPDT analogmultiplexing switch U3 within the feedback loop, which increases gain asPWM0 is increased. The IRAC and REDAC are then filtered and input to theCPU, and can be measured at TP55 and TP59, respectively.

9.6 DIGITAL CIRCUITRY

The digital hardware and related circuitry, which is illustrated in Figure 9-14,includes the following subsystems:

• CPU — A 16-bit microcontroller that includes: a serial port, watchdogtimer, A/D converter with an 8-input analog multiplexer, 3-pulse widthmodulators, and a high speed I/O subsystem.


9-13

• System memory — System memory is external to the CPU and consists ofan 8K × 8 static RAM and a 64K × 16 EPROM.

• Real-Time Clock (RTC) — The RTC keeps track of date and time, which isprinted on each printout. A lithium battery designed to last up to 5 yearsbefore needing replacement powers the RTC.

• Audio output — A piezoelectric ceramic beeper is used for audio output.

• Display control — A high-visibility display provides oxygen saturation andpulse rate values. An ambient light sensor responds to low-light conditionsand turns on the display backlight.

• User controls — A On/Off button and a battery-check button. The On/Offbutton signals the power control circuit to switch on the power supply. Pressand hold the battery-check button to display a percentage of useful liferemaining in the batteries.

• Power supply/Power control circuitry — The N-20PA receives powerfrom 4 “C” cell batteries. The power control circuitry discontinues power tothe unit when the batteries are no longer reliable.

• Thermal printer — Generates a hard copy of oxygen saturation and pulserate values. A sensor monitors ambient temperature and adjusts printeroutput to ensure consistent print quality.

MeasureCheck Battery

Power supply& control

N-20/N-20P Control buttons

AUXPCB Ambient

light sensorMainPCB

CPU

Main PCB

Memory&

software

To analog section

Real-timeclock

AUXPCB

Ambienttemp. sensor

MainPCB

ON ADV D/D

Printer

Audio beeper

(N-20 only)

Displaydrivers

Printer Control button

AUX PCB

Display

AUX PCB

Figure 9-14: Digital Circuitry Block Diagram

9.6.1 CPU

The CPU circuit is illustrated in Figure 9-15, at the end of this section.

The Intel 80C196KC CPU is a 16-bit microcontroller with built-in peripheralsincluding a serial port, watchdog timer, A/D converter with an 8-input analogmultiplexer, three pulse width modulators, two 16-bit counter/timers, up to 48I/O lines, and a high speed I/O subsystem.


9-14

The CPU is capable of running up to 16 MHz; however, it is run at 10 MHz fordecreased power consumption. All unused inputs are tied to either Vcc orground through resistors—this prevents unused inputs floating to any voltageand causing excess power drain. The READY input pin is tied high, therebydisabling wait-state generation; all bus accesses are zero-wait state. The EA pinis tied low to enable addressing of the external EPROM.

When the power supply is first switched on by the power control circuit, thereset generation circuit holds the CPU RESET pin low for at least 20 ms, thenallows the internal pull-up resistor to bring it high; this assures a good CPUreset.

An internal watchdog timer is enabled and runs continuously. The watchdogtimer provides a means of recovering from a software glitch caused by ESD,EMI, and so forth. If the software does not clear the timer at least every 64Kstate-times (13.1 ms), the CPU will drive RESET low, resetting the entire unit.The reset output by the CPU is only 16 state-times long (3.2 µs). Q22 providesisolation from C65 so the CPU can drive a good reset to the display controlcircuit.

The CPU has the ability to dynamically switch the data bus width—based on theBUSWIDTH input pin. A low on BUSWIDTH tells the CPU to access memoryonly 8 bits at a time. When accessing the static RAM, BUSWIDTH is low,automatically reading the 8-bit wide RAM. Since BUSWIDTH is connected tothe active low RAM enable line (RAMEN), all other memory and mapped I/Oare read or written 16 bits at a time.

The CPU measures eight analog inputs. Input from the SpO2 analog sectionincludes AC and DC signals for the oximeter sensor red and infrared channels,and the sensor calibration resistor RSENS. Light, temperature, and batteryvoltage are also measured.

The N-20PA CPU is configured as follows:

• Decoded AD0 and BHE generate separate WR write strobes for the low andhigh bytes of a word. The signal WR (pin WRL) is the low-byte writestrobe.

• A standard address latch enable (ALE) is generated and used.

• HSO pins 4 and 5 are configured as outputs. The HSO is used to generatestable timing control signals to the SpO2 analog section, display, and printer.

• The timer-2 external control pins: T2CLK, T2RST, T2U-D, and T2CAPT—are disabled via software and used as standard I/O.

• The HOLD, HLDA, and BREQ bus accessing is disabled via software andthe pins are used as standard I/O.

• Pins HSI0 and EXTINT are configured for interrupt input. The CPUreceives 2 external interrupts (signals PR_TACH and PHOTOI).

• RXD and TXD are configured as a standard asynchronous serial transmitterand receiver for the serial interface.

• PWM0, PWM1, and PWM2 pins are configured as pulse width modulatoroutputs. They are used to control gains within the SpO2 analog section.

9.6.1.1 Address Demultiplexing

The address demultiplexing circuit is illustrated in Figure 9-16.


9-15

10KR109

TP40

TP39

AD15AD14AD13AD12AD11AD10AD9AD8

ALE

ALE

AD7AD6AD5AD4

74HC573

U33

1OC

11C

12Q8

9D8

13Q7

8D7

14Q6

7D6

15Q5

6D5

16Q4

5D4

17Q3

4D3

18Q2

3D2

19Q1

2D1

10KR108

A15A14A13A12A11A10A9A8

A7A6A5A4

74HC573

U13

1OC

11C

12Q8

9D8

13Q7

8D7

14Q6

7D6

15Q5

6D5

16Q4

5D4

17Q3

4D3

18Q2

3D2

19Q1

2D1

A3A2A1A0

ADDRESS DEMUX

AD3AD2AD1AD0

Figure 9-16: Address Demultiplexing Circuit

U13 and U33 are transparent latches that latch the address portion of the AD busdata on the falling edge of ALE; the outputs are always enabled. The outputs ofU13 and U33 are always the address portion of the AD bus.

9.6.1.2 Address Decoding

The address decoding circuit is illustrated in Figure 9-17.

The CPU has a 64 Kbyte address range of 0-FFFF. RAM, EPROM, and I/Oports share this space. The address decoding circuit splits up this space andoutput enable lines to the RAM, EPROM, and I/O ports.

U30A generates the static RAMs active low enable signal, RAMEN. Whenaddress lines A13, A14, A15 are all high, U30A’s output goes low, enabling theRAM. This occurs for the 8K address range of E000-FFFF.


9-16

A10

A11

TP71

A15ROMEN

10K

R134

0000-DBFF

VCC

74HC10

U30C

8 11 10 9

74HC10

U30A

12 13 2 1

TP74

RAMEN

TO: N-20

AUX PCB

DC00-DFFF

E000-FFFF

74HC10

U30B

6 5 4 3

74HC138

U28

7Y7

9Y6

10Y5

11Y4

12Y3

13Y2

14Y1

15Y0

5G2B

4G2A

6G1

3C

2B

1A

A14

ADDRESS DECODING

WR

A14A15

A13

RD

A12

EXOUTEN

EXINEN

20 HDR

20

19

Figure 9-17: Address Decoding Circuit

U30B and U28 are used to generate the input port and output port active lowenable signals EXINEN and EXOUTEN. When address lines A15, A14, A11,and A10 are high, and A13 is low, U28 becomes enabled. With U28 enabled,one of the 8 outputs is set low. The output to go low is selected by pins A, B,and C. They form a 3-bit binary number with pin C being the most significantbit. So when address line A12 is high, WR active (low) and RD inactive (high),a binary 5 is produced on pins A, B, and C, forcing output Y5 (EXOUTEN) low.This enables the output port for writing. When address line A12 is high, WRinactive and RD active, a binary 3 is produced on pins A, B, and C, forcingoutput Y3 (EXINEN) low. Note that in both previous conditions, A15, A14,A12, A11, and A10 are high and A13 is low.

The input port and the output port both share the same 1 Kbyte address space ofDC00-DFFF. When data are written to that address, the output port enablesignal EXOUTEN is activated. But when data are read from the same address,EXINEN is activated. Because the CPU is configured to use a 16-bit bus, exceptfor RAM, any even address in the DC00-DFF range could be used for externalport access. In other words, reading or writing address DC00, DC02, DC04, andso on, will all produce the same results. Due to the CPU configuration, the writestrobe WR (WRL pin), is only active for low-byte writes; therefore, both bytesof the external output port must be written to at the same time. Because, theupper byte of the output port cannot be written to alone, no write strobe and,therefore, no EXOUTEN signal will be generated.


9-17

U30C generates the EPROMs active low enable signal, ROMEN. The activelow signals RAMEN and EXINEN are basically used as EPROM disable signals.When RAMEN or EXINEN or test point TP71 are low, the output of U30C,ROMEN, is forced high, disabling the ROM. Therefore, the EPROM is disabledfor the range DC00-FFFF and enabled for the 55 Kbyte address range of0h-DBFF. TP71 is used during board testing to disable the EPROM.

9.6.2 CPU Memory

The CPU memory circuit is illustrated in Figure 9-18.

AD7AD6AD5AD4AD3AD2AD1

AD15AD14AD13AD12AD11AD10

AD9AD8

ROMEN

VCCVCC

RD

A15A14A13A12A11A10A9A8A7A6A5A4A3A2

TP43

27C1024L

U15

4O15

5O14

6O13

7O12

8O11

9O10

10O9

11O8

14O7

15O6

16O5

17O4

18O3

19O2

20O1

21O0

43PGM

2VPP

22OE

3

41A15

40A14

39A13

38A12

37A11

36A10

35A9

32A8

31A7

30A6

29A5

28A4

27A3

26A2

25A1

24A0

RAMEN

WR

64K X 16 EPROM

A1

A12A11A10A9A8

RD

A7A6A5A4

10KR133

VCC

AD0


U14

19D7

18D6

17D5

16D4

15D3

13D2

12D1

11D0

22OE

27WE

26CS2

20CS1

2A12

23A11

21A10

24A9

25A8

3A7

4A6

5A5

6A4

7A3

8A2

9A1

10A0

8K X 8 SRAM

A3A2A1A0

CE

Figure 9-18: CPU Memory Circuit

The memory system external to the CPU consists of an 8 K × 8 static RAM(U14) and a 64 K × 16 EPROM (U15). The EPROM is 16 bits wide to enhanceCPU performance. Because RAM is infrequently accessed, it is only 8 bits wide.

U14 is a standard 8K × 8 static RAM. Test point TP 43 is used during testing todisable the output.


9-18

The program that the CPU runs is stored in U15. U15 is a 16-bit wide output,one-time programmable (OTP) EPROM. During 16-bit wide bus accesses, theCPU uses address line A0 for low/high byte selection. A0 is not used as anormal address line. The CPU can only address 64K × 8 bytes or 32K × 16bytes. Pin A15 of U15 is tied low, always selecting the lower half of theEPROM. Signal ROMEN is then used to enable the EPROM for the propermemory area.

9.6.2.1 Input Port

The input port circuit is illustrated in Figure 9-19.

EXINEN 74HC573

U16

1OC

11C

12Q8

9D8

13Q7

8D7

14Q6

7D6

15Q5

6D5

16Q4

5D4

17Q3

4D3

18Q2

3D2

19Q1

2D1

EX_IN INPUT PORT

RTC_IOBAT_TYPEPR_HOMEADV_BTNDD_BTNON_OFF_BTN

GO_BTN

VCC


Figure 9-19: Input Port Circuit

U16 is the input port external to the CPU. The logic levels on the inputs (pinsD1-D8) are output to the CPU via the AD bus while EXINEN is strobed low. Allof the user control buttons are input via U16. Also, the battery type is senses viaU16; a high on signal BAT_TYPE signifies to the CPU that rechargeablebatteries are being used. If the optional printer head is in the home position,PR_HOME will be a logic high.

Pin D8 (RTC_IO) and an output bit of the external output port are connected.They work as a pair to create a bidirectional bit for communicating with the RTC(see Section 6.3, Real-Time Clock and Non-Volatile Memory).

9.6.2.2 Output Port

The output port circuit is illustrated in Figure 9-20, at the end of Section 9.

The output port external to the CPU consists of 2 octal D latches, U18 and U17;they function as a single 16-bit output port. U18 is the lower byte (LSB) andU17 is the upper byte (MSB). The output of U18 is always enabled. The outputbits of U18 control audio output, optional printer, RTC, and display.


9-19

The signal PR_STROBE controls U17’s output drivers. Under normal operation,the outputs are tristated and resistors R148-R154 pull the outputs low.PR_STROBE is driven low to turn on the output drivers of U17. SignalsPR_DOT0-PR_DOT6 (pins Q1-Q7) drive the 7 print dots of the optional printer.PR_STROBE pulses all 7 of the dot lines for a specific time period (see alsoPrinter Interface, Section 6.14). When the CPU is first powered on,PR_STROBE is in a tristate condition. R123 assures that U17 does notaccidentally turn on the printer head dots until required to. Pin Q8 (RTC_IO)and an input bit of the external input port are connected. They work as a pair tocreate a bidirectional bit for communicating with the RTC (see also “Real-TimeClock and Nonvolatile Memory”).

Both bytes of external output port (that is, U18 and U17) must be written to atthe same time. The upper byte of the output port (U17) cannot be written toindependently (see also “Address Decoding”).

9.6.3 Real-Time Clock (RTC) and Nonvolatile Memory

The Real-Time Clock Circuit is illustrated in Figure 9-21.

3.32K

R163

1N914

CR23

1N914CR22

DS1202S

U29

8 5 3

16

9RST

12I/O

14SCLK

TEST

TP76

.1uF

C114

32.768KHz

Y1

3VBT1

TEST

TP86

TEST

TP87

TEST

TP85

RTC_RST

RTC_IORTC_CLK

REAL TIME CLOCKVCC

GND

X1VCC

X2

Figure 9-21: Real-Time Clock Circuit

The RTC has two functions: (1) it provides nonvolatile memory that is used toremember whether the printer should be enabled at power-on, and (2) to keeptrack of time and date for the N-20PA printer. The N-20PA does not require oruse the RTC; it is disabled via software.

The RTC chip U29 uses a 3-wire synchronous serial interface to communicatewith the CPU. The CPU brings signal RTC_RST high to activatecommunication with the RTC. RTC_CLK clocks data into and out of the RTCchip. RTC_IO is the bidirectional communication data bit. The CPU drivesRTC_IO when writing data and commands to the RTC. The CPU tristatesRTC_IO and then reads data back onto it from the RTC.


9-20

Crystal Y1 provides an accurate 32.768 KHz clock input whenever thetimekeeping circuitry of U29 is activated. The CPU only enables thetimekeeping function when an optional printer is installed. If no printer isinstalled, the CPU switches off timekeeping, thereby extending battery life.Also, with no printer installed, the RTC clock is only used during diagnostictesting to verify the CPU clock timing.

The lithium battery BT1 and diodes CR22 and CR23 provide the power switchover and constant power needed to keep the time and RAM data while the unit isnot in use. Whenever the unit is powered on, Vcc is at 5 V and U29 is poweredvia CR22. CR 23 is reverse biased because BT1 at 3 V is at a lower potentialthan Vcc. Whenever the unit is powered off, the potential between Vcc andswitched ground is 0 V, CR23 is forward biased, and U29 is powered by BT1.CR22 is reverse biased, isolating BT1 from Vcc. This circuit design allows BT1life of up to 5 years typical, without the unit being powered on.

U29 holds 24 bytes of RAM, which is used for nonvolatile storage of CPU data.

9.6.4 Audio Output

The audio output circuit is illustrated in Figure 9-22.

TESTTP75 TEST

TP74

BEEPER

BEEP_2BEEP_1

AT17

BZ1

Figure 9-22: Audio Output Circuit

BZ1, a piezo ceramic sounder, is the audio output device. Due to its low drivecurrent of 2 mA maximum, no drive circuitry is needed and is driven directlyfrom the external output port. The audio output device is differentially drivenwith 2 square waves 180 degrees out of phase. The drive frequency isapproximately 1480 Hz or 740 Hz and is generated by the CPU. BZ1 isdifferentially driven to obtain maximum audible volume.

9.6.5 Display Control Circuitry

The display control circuit is illustrated in Figure 9-23, at the end of Section 9.Figure 9-5 shows the display control block diagram.

The Taliq display is controlled by the display control circuitry. A photosensormeasures ambient light and automatically switches on the electroluminscentdisplay backlight during low-light conditions. The display control circuitry isdivided into the following subsections:

• Control Conditioning Circuit (main PCB) — The control conditioningcircuit processes signals generated by the CPU to produce timing signals forthe display drivers.

• Display Driver ICs (auxiliary PCB) — Each of the two display driver ICshave 32 high-voltage outputs that enable individual segments of the displayto be turned on or off.


9-21

• High Voltage Control Circuit (auxiliary PCB) — The high-voltage controlcircuit allows the CPU to switch on or off the display’s high-voltage input.

9.6.5.1 Control Conditioning Circuit

The CPU generates a 400 µs low-pulse train at a 160 Hz rate on signalDISP_PHASE. Half of U34 takes DISP_PHASE as an input and createsDISP_POL as an 80 Hz 50% duty cycle square wave. A CPU reset initializesDISP_POL low when any CPU reset occurs so the software knows the initialstate. The other half of U34 is used to synchronize the rising edge of theDISP_DL with the rising edge of DISP_POL. The CPU brings DISP_LATCHsignal high before the rising edge of DISP_PHASE; this allows the high to beclocked out to DISP_DL on the rising edge of DISP_PHASE. About 100 µsafter the rising edge of DISP_PHASE, the CPU brings DISP_LATCH low,asynchronously resetting DISP_DL low.

9.6.5.2 Display Driver Control Circuits

U19 and U20 are the display segment driver chips. Each chip has 32high-voltage outputs and a common display marked BP (backplane). The CPUvia a serial shift register input inputs the display data to U19 and U20. U19 andU20 are daisy-chained together forming a 64-bit serial shift register. Displaydata are loaded and shifted down via the DISP_DATA and DISP_CLK signals.When all 64 bits of the shift register are loaded, a high pulse on DISP_DLupdates the display, all 64 bits at the same time. The display is clocked with an80 Hz 50% duty cycle waveform by signal DISP_POL. DC voltages cannotdrive the display or display damage will result. Creating a 180-degree phaseshift between the segment pin and the BP common pin illuminates displaysegments. Segments are left dark by making the waveform on the segment pinbe in phase with the BP pin. The display has an electroluminescent (EL)backlight, and is driven the same as the display segments. Connectors JP2, JP3,and JP5 connect the display and EL backlight to the drive electronics.

9.6.5.3 High Voltage Control Circuit

The cold switch circuit performs two basic functions: (1) it allows the CPU toenable and disable the display high voltage VDISP, and (2) it slows the edgeslew rate of the segment drivers as it switches the high voltage. When the signalDISP_PHASE is low, Q14 is disabled, pulling VDISP low. Whenever the CPUis powered on, DISP_PHASE is tristated. The base emitter junction of Q12 pullsDISP_PHASE low, disabling the high voltage. This assures that the high voltageis only enabled to the display when controlled by the CPU.

The Taliq display is similar to an LCD in that the load of a segment is mainlycapacitive. A cold switch circuit provides a current-limited 70 V to VDISP.R93, R95, Q21, and Q14 do the on/off switching and current limiting. As thedriver chips’ output waveforms and DISP_PHASE change states, the capacitiveloads of the display cause VDISP to limit current until the capacitance is fullycharged. This constant output current is integrated into the display capacitiveloads, causing a highly linear rising and falling voltage ramp on VDISP.Because the high voltage to the drive chips (VDISP) is ramped, the outputs ofthe driver chips U19 and U20 are also ramped at the same controlled rate. Thisdesign is used to reduce current spikes on the 70 V power supply, and, inaddition, to reduce the EMI generated by the display due to the lower slew ratesof the high-voltage switching signals.


9-22

9.6.6 Standard User Controls

The user-controls circuit is illustrated in Figure 9-24.

The standard user controls consist of two momentary push-button switches(On/Off and battery-check). The Of/Off button is an elastomeric contact switch,and the battery-check button is a mechanical momentary switch.

The CPU input lines BAT_BTN and GO_BTN are normally pulled to the highstate by R71 and R78. Whenever a button is pressed, the CPU input line ispulled low through R74 and R80. The switch contacts are debounced with C64and C66. L11, L12, C126, and C123 provide a current path for ESD protection.

In addition to being read by the CPU, the On/Off button also activates the powersupply via the power control circuit. Note that the On/Off button has circuitryon both the main PCB as well as the auxiliary PCB.


9-23

S2MEASUREBUTTON

221

R80JP8

2

1

TO: N-20AUX PCB

GO_SW

TEST

TP81

TEST

TP88

100PFC126

L12

SW1 .01UFC64

1K

R74BAT_BTN

CHECK BATTERY

150KR71

VCC

JP18

2

1

L11GO_SW

TESTTP71

100PF

C123

3.32KR79

15KR102

TEST

TP72

GO_BTN

VCC

.01UFC66

VCON

150KR78

MAIN PCBTO: N-20

GO BTN

To U21pin 4

Figure 9-24: User Controls Circuit

Power Supply/Power Control Circuitry

Power supply circuitry is located on the auxiliary PCB and consists of thefollowing subsections:

• Batteries — Four 1.5-V alkaline “C” size batteries provide 4–6 VDC power.

• Power control circuitry — Power control circuitry is connected to thebatteries. It senses any press of the On/Off button and switches on the powersupplies. Reverse current limiting protects the N-20PA from damage ifbatteries are inserted incorrectly.


9-24

• Power shutoff circuit — This circuit controls power to all circuits except thepower control circuit. In addition, a fuse protects the power supply fromexcessive current draw. The power supply is also protected againstelectrostatic discharge and electromagnetic interference.

• Power supply circuits consist of the following power supplies:

Regulated power supply: Power supplied by the batteries is regulatedat 5 VDC. This supply is used by all of the digital circuitry and some ofthe SpO2 analog circuitry.

Unregulated power supplies: 5 VDC is converted by a switchedcapacitor network into unregulated power supplies of -5 VDC, 10 VDC,and 12 VDC, all of which are used in the SpO2 analog circuits.

High voltage power supply: A voltage regulator/doubler convertsbattery power to 70 VDC; this increase in power is needed by thedisplay drivers as well as the display backlight.

The power supply circuit is illustrated in Figure 9-25, at the end of Section 9.Figure 9-4 shows the power supply block diagram.

9.6.7.1 Power Control Circuitry

The power control circuit is illustrated in Figure 9-26, at the end of Section 9.

The power control circuit consists of U21 and its associated components. U21 isa D flip-flop with asynchronous preset and clear; only the preset and clear areused.

Power is applied to U21 via CR11 whenever batteries are installed. CR11provides protection for U21 if the batteries are installed with reverse polarity.This error condition will reverse bias CR11, thereby disabling current flow toU21.

The much larger RC time constant of R110, C67 compared to R78, C66guarantees that the unit will not be accidentally powered-on when batteries arefirst installed.

Whenever the measure button is pressed, a low on GO_SW sets the output signalPWR_ON high. This condition connects switched and battery grounds, enablesthe power supplies, and switches on the unit. Whenever the CPU determinesthat the power should be switched off, it forces PWR_DOWN low. This actionclears output PWR_ON to a logic low, disconnecting ground, and switching offthe power supplies (see also “Power Supply”).

R79 and R81 provide current limit protection to U21 inputs. They also limit thecurrent that will flow through U21 inputs to the CPU when the batteries areinstalled backward. In the reverse battery error condition, excessive current canflow from the inputs of U21 through the input protection diodes or substrateinside the CPUs integrated circuit or through both. These resistors limit thatcurrent path to safe levels.


9-25

9.6.7.2 Power Shutoff Circuit

This circuit is illustrated in Figure 9-25, Power Supply Circuit.

Fuse F1 protects the unit from excessive current draw. CR24 protects againstlarge voltage transients caused by ESD, EMI, and so on.

Q15 is a dual-channel FET; the drain of Q15 part 2 (pin D2) is connected tobattery ground; the gate (G2) is connected to battery plus; and R155 applies abias to the source (S2) so it will switch on when a positive voltage is applied toG2. When batteries are correctly installed, Q15 part 2 is switched on andconducts current. If batteries are installed backward, Q15 part 2 switches off anddisables current flow. This protects the unit’s power supply circuitry from anaccidental reversal of battery potential.

Q15 part 1 controls the power supplies. When a logic high is placed on the gate(pin G1) signal PWR_ON battery ground is connected to the circuit and switchedto ground via Q15 parts 1 and 2. When the power control circuitry pullsPWR_ON low, switched ground switches to a high impedance state. This actionswitches off the power supply and, therefore the unit, except for the powercontrol circuit.

9.6.7.3 Vcc Power Supply


The Vcc power supply is a switched inductor voltage regulator operating inboost mode (U22). The power input is provided by the batteries (VBAT).NFET (Q17) operates as a linear post regulator. The 1 M resistor (R77) operatesas a static bleed device across the switched regulator when the regulator isswitched down. The regulated output is Vcc (5 V ± 5%).

9.6.7.4 Raw Power Supplies


The input to the raw power supplies is Vcc, which is a switched-capacitorvoltage converter operating in separate multiply and invert modes in conjunctionwith supporting circuitry. U23 inverts Vcc and outputs raw –5 V. Raw 10 V isderived by voltage doubling Vcc with CR14, CR19, CR20, and CR78. Raw 12V is derived by voltage tripling Vcc with CR15, Q8, Q9, C96, C81, R119, andR120.

The raw power supplies are used as bias supplies for the SpO2 analog sectionand are not tightly regulated. The normal operating range of the raw powersupplies are:

raw –5.0 V = –6.0 V to –4.0 Vraw 10.0 V = 7.5 V to 11.0 Vraw 12.0 V = 12.0 V to 15.0 V


9-26

9.6.7.5 High Voltage Supply


The batteries (VBAT) provide the input power for the high-voltage supply. Thehigh-voltage supply is a switched-inductor voltage regulator (U26) that operatesin conjunction with a capacitive voltage doubler to output 72 VDC ± 5%. Toprotect against a runaway voltage condition, CR25 clamps U26 output to a safelevel.

9.6.8 Analog Reference Voltage

The analog reference voltage circuit is illustrated in Figure 9-27.

U32 provides an accurate, regulated voltage that is used as the reference voltagefor the A/D converter inside the CPU. C6, C12, and R124 provide filtering. Thevoltage output VREF is 5 V.

+5.7

2N3904Q24

VREF

TP62

TP61

-5V

22UFC93

+12V

22UFC91

221

R122

221

R121

RAW-5V

0.1UFC94

RAW12V

0.1UFC80

182

R123RAW10V

22UFC95

10K

R161

2N3904Q23

TP60

GNDTP70

1

R124

22UFC12

LT1021

U32

5TRIM

6VOUT

4GND

2VIN

VREF

0.1UFC6

Figure 9-27: Analog Reference Voltage Circuit


9-27

9.6.9 Ambient Light

The ambient light circuit is illustrated in Figure 9-28.

33.2KR136

TP72

.01UFC63

2.2MR68

MMBTA13LQ8

VCC

VTB8442BD8

LIGHT SENSOR

VCC

AmbientLight

Figure 9-28: Ambient Light Circuit

Diode D8 is a photodiode that is used to measure ambient light. Q8, R68, andR136 provide current gain for D8’s photocurrent. The amplified photocurrentflowing through R136 creates a voltage drop, which is measured by the CPU.The CPU continually monitors the light source output at AMB_LIGHT (TP72).Under low-ambient light conditions, the CPU automatically switches on thedisplay backlight.

9.6.10 Ambient Temperature

The ambient temperature circuit is illustrated in Figure 9-29.

0.1uFC115

LM35

U5 1

VCC

3GND

2TEMP

TEMP SENSOR

VCC

PR_TEMP

Figure 9-29: Ambient Temperature Circuit

U5 is a precision-temperature sensor. It outputs (PR_TEMP) a voltageproportional to the ambient temperature, which is 10 mV per degree centigrade.For example, at a room temperature of 25 °C, the U5 output would be 250 mV.U5 is used to compensate for ambient temperatures associated with thermalprinters.


9-28

9.6.11 Battery Voltage

The battery voltage circuit is illustrated in Figure 9-30.

.01UFC62

1%47.5K R70

BATTERYVOLTAGESENSE

BAT_VOLT

TP73

1%15.8K R69

VBAT

Figure 9-30: Battery Voltage Circuit

The analog input voltage range of the CPU is 0-5 VDC. Because the batteryvoltage may be as high as 6.2 V, R69 and R70 form a voltage divider to decreasethe measured battery voltage to a usable level. The gain is 0.75; thus, if thebattery voltage was 6 V, then the voltage of BAT_VOLT would be 6 × 0.75which equals 4.5 V.

The software has the ability to determine when battery power is too low. If thesoftware determines that the battery voltage is too low to provide accurateinformation, the software generates an audible signal and automatically switchesthe unit off. The battery voltage data are also used to compensate for batteryvoltage changes that can affect printout quality.

9.6.12 Battery Type

The battery type circuit is illustrated in Figure 9-31.

BAT_TYPE

1N914CR27

150KR101TEST

TP2

15K

R100VRECHARGE

VCC

N-20AUXPCB

Figure 9-31: Battery Type Circuit

The unit operates on disposable batteries. Battery type input is digital; a highinput informs the CPU that rechargeable batteries are in use. If rechargeablebatteries are used, the battery and the VRECHARGE terminals are mechanicallyconnected. This applies the battery voltage to VRECHARGE, pullingBAT_TYPE high. R100 and CR27 are a current-limiting resistor and avoltage-clamping diode that are used to protect the input port from excessivebattery voltage. If disposable batteries are used, VRECHARGE is electricallyisolated, which allows R101 to pull BAT_TYPE input low.


9-29

The nominal voltages and voltage discharge curves are significantly differentbetween rechargeable and disposable batteries. In order for the CPU to predicthow much “battery life” remains, the nominal voltage and discharge curves mustbe known; the BAT_TYPE signal provides that information

9.6.13 Printer Control

Printer circuitry is divided into two subsections: the printer interface and theprinter flex circuit.

• Printer interface circuit (auxiliary PCB) — This circuit detects thepresence of the flex circuit, and supplies power to the print heads and paperadvance motor. Noise generated by the printer motor is filtered. Thecircuitry is protected from excessive battery currents by a fuse.

The printer interface circuit is illustrated in Figure 9-32, at the end of Section 9.

• Printer flex circuit — The printer flex circuit is added when the printer ispresent. The printer generates a timing signal that is read by the CPU andsent to the flex circuit. This circuit signals the CPU that a printer is presentby connecting one CPU input to ground. Power and power control signalsfrom the auxiliary PCB generate an output load for a resistor array; heatfrom this process produces a dot matrix pattern on thermal paper.

The printer flex circuit is illustrated in Figure 9-33, at the end of Section 9.The printer control block diagram is shown in Figure 9-6.

User control is provided by momentary push buttons: ON (on/off), ADV(advance), and D/D (day/date). ON enables or disables the printer, ADV controlsthe advance of printer paper, and D/D sets date, time, and other clockparameters.

When a low battery voltage condition is present, the N-20PA adjusts power tothe printer’s head; however, a weak battery voltage condition causes the printerto shut off, thereby allowing the N-20PA to continue to display oxygensaturation and pulse rate readings until the batteries are exhausted. An ambienttemperature sensor adjusts printout quality to compensate for environmentalconditions.

9.6.13.1 Printer Interface Circuit

The printer interface circuit is illustrated in Figure 9-32, at the end of section 9.

The following is a description of the printer interface circuitry found on allN-20PA auxiliary PCBs.

The CPU reads the PR_PRESENT signal to determine if a printer is installed.With PR_PRESENT left floating, it is pulled high by the weak pull-up resistorinside the CPU. If a printer is installed, PR_PRESENT is connected to switchedground, which causes a low input to the CPU. The optional printer circuit isprotected from excessive battery currents by fuse F2. CR28 is used to blocknoise generated by the printer motor being injected onto the batteries.

The N-20PA printer is a 16-character-wide thermal dot matrix printer, whichgenerates a CPU interrupt for every dot column. The thermal energy given to theprint head is controlled by the pulse width of the active high signals PR_DOTx.In order to provide consistent print quality, the ambient temperature, print drivevoltage, and print head resistance must be measured and accounted for.


9-30

Inside the print head are seven resistors that heat up when power is applied, andin turn create dark dots on the thermal paper. One lead of the print-headresistors is connected to the printer supply voltage VPRN; the other lead isconnected to the driver chip (see “Optional Printer Flex Circuit with UserControls”). One of the print dot resistor leads (DOT4) is also fed back to theprinter interface circuitry. The DOT4 signal is a print dot resistor with a rangeof 11-16 ohms, which is connected to VPRN.

The print head resistance is measured by U36. R143, R144, R145, R146, andhead resistor DOT4 form a two-level resistor bridge. The resistor bridge isswitched on when PR_MEAS is pulled high, pulling TP77 low and biasing theresistor bridge. The logic outputs of PR_HEAD1 and PR_HEAD2 are read in bythe CPU to determine the head-resistance category of this particular head. R156ensures that Q20 does not switch on when the batteries are installed backward.Due to the large current draw of the resistor bridge and the fact that the headresistance does not change significantly over time, the head resistance is onlymeasured once at every power-on.

The CPU starts the printer motor running by setting PR_MOTOR high. A singlemotor drives both the print head and paper advance mechanisms. The printerprovides a printer timing generator (TG) signal, which is an AC waveform ofabout 4 Vpp. Q19, R106, R142, and CR29 convert the AC waveform to aCMOS level square wave; this signal (PR_TACH) is then used as a CPUinterrupt line. An interrupt routine services the printer, thereby producing therequired dot patterns to create the characters. C127 is used to filter noise.

The position of the print head is sensed by the signal PR_HOME. Whenever theprint head is not in the home position, a switch in the printer closes, shortingPR_HOME to switched ground. Whenever the print head is in the homeposition, the switch opens, allowing R118 to pull PR_HOME high.

The print head dot pattern and pulse width are controlled by the CPU. Theproper printer dot values are loaded into the output port, then the proper pulsewidth is loaded into the CPU CAM for PR_STROBE. The signal PR_STROBEenables the outputs for the specified pulse width. When the PR_DOTX lines arehigh, a dot will be printed.

9.6.13.2 Printer Flex Circuit and User Controls

The printer flex circuit is illustrated in Figure 9-33, at the end of section 9.

The thermal printer is plugged in via connectors JP10 and JP11. ThePR_PRESENT signal is connected to switched ground to tell the CPU that aprinter is installed. U1 is a Darlington pair driver chip that is used to drive theprinter dots and motor. When an input is high, the output is shorted to ground,driving the output load.

The auxiliary PCB provides constant power (VPRN) and a power control line(PWR_ON). Q1 is used as a power control FET. Both halves are used inparallel to reduce the on resistance. When PWR_ON is high, the sources (S1,S2) short to the drains (D1, D2), connecting ground to U1 and C3. PWR_ONalso controls the regulated power supplies; thus, Q1 and the power supplies areboth enabled and disabled at the same time.


9-31

The large bulk capacitor C3 is required due to the large current spikes that arerequired by the printer and the large internal series resistance of disposablebatteries. Bulk capacitance is required to lessen the battery voltage drop causedby the current spikes.

The N-20PA has three additional user-control buttons. L8, L9, L10, C120,C121, and C122 provide ESD protection. R103, R104, and R105 providepull-ups when the user buttons are open. These pull-up resistors are in theprinter interface circuit to ensure that the buttons (ON, ADV, and D/D) are neverleft floating, regardless of whether an optional printer flex circuit is installed ornot.

The optional user controls consist of three momentary push-button elastomericcontact switches. Pull-up resistors are provided by the printer interface circuitry.R1, R2, and R3 help protect the input port by providing some current-limitingcapability. C4, C5, and C6 debounce the switch contacts.

9.7 CIRCUIT ILLUSTRATIONS

The foldout graphics referenced throughout the Technical Supplement text are asfollows:

Figure 9-8: LED Drive Circuit

Figure 9-10: N-20PA HSO Timing Diagram

Figure 9-13: AC Variable Gain Control Circuit

Figure 9-15: CPU Circuit

Figure 9-20: Output Port Circuit

Figure 9-23: Display Control Circuit

Figure 9-25: Power Supply Circuit

Figure 9-26: Power Control Circuit

Figure 9-32: Printer Interface Circuit

Figure 9-33: Printer Flex Circuit

Figure 9-34: N-20PA Main PCB Schematic Diagram

Figure 9-35: N-20PA Auxiliary PCB Schematic Diagram

Figure 9-36: N-20PA Flex Circuit Schematic Diagram

9-33

Figure 9-8LED Drive Circuit

TO CENTER MTG. HOLE

TP48

6.04KR18

.01UFC5

RSENS

MMBTA06

Q2

2N3904Q510K

R47

IR/RED

1N914

CR181N914

CR12

22PFC123

100K

R162

100K

R49

20KR44

.022UF

C38

.1UFC37

LT1013

U9A

2

6

7 8

1 280KR423.74K

R135

4.7PF

C60

182KR5020K

R43

.022UF

C39.1UF

C53

VCC

VCC

100K

R53

100K

R52

.1UFC36

MMBTA56Q3

6.8R54

10KR48MMBTA06

Q1

MMBTA56Q4

22.1K

R51

TP50

TP46

LED DRIVE

10KR46

10K

R64

.1UF

C55

4053

U10

7VEE

8VSS

16VDD

4Z

15Y

14X

9C

10B

11A

6INH

3Z1

5Z0

1Y1

2Y0

13X1

12X010K

R45

VCC

100PF

C118

100PF

C119

100PF

C117

100PF

C116

L5

L3

L4

TP45

TP47

SENSORINPUT

VREF

VREF

DB9F

P1

1 6 2 7 3 8 4 9 5

TP77

TP83

TP84

RSENS

LED DIS

OFF/ON

IR/RED

PHOTOI

PWM1PWM2

9-35

Figure 9-10N-20PA HSO Timing Diagram

OFF/ON(HSO.1)

/SAMPIR(HSO.2)

/SAMPRED(HSO.0)

IR/RED(P1.1)

µS

State Time

0

0

105.6

66

158.4

99

177.6

111

283.2

177

336.0

210

337.2

211

443.2

277

496.0

310

515.2

322

620.8

388

673.6

421

-60µS-60µS

9-37

Figure 9-13AC Variable Gain Control Circuit

15KR5

3.32K

R33

3.32K

R21

TP59

TP58

TP57

.47UFC31

.1UF

C30

IRAC

REDLED/AV

/ZERO

IRDC

.01UFC8

PWM0

12.1K

R31

3.32KR66

3.32KR61

LMC6044

U7D

14 13

12

LMC6044

U7B 7

6

5

34.8K

R37

100K

R36

.01UF

C111

.01UFC57

1NF

C32VREF

LTC201U11D

7

68

.015UFC29

15KR41

12.1K

R22

RED

3.32K

R60

3.32K

R29

47.5KR40LMC6044

U7C 8

9

10

LMC6044

U7A

11

4

12

3

34.8K

R28

100K

R30

1NFC28

VREF

LTC201U11C

.015UFC9

TP56

TP55.47UFC27

.01UFC56

.1UF

C58

4053

U3

7VEE

8VSS

16VDD

4Z

15Y

14X

9C

10B

11A

6INH

3Z1

5Z0

1Y1

2Y0

13X1

12X0

VCC

PWM1

.1UFC26

REDAC

3.32K

R20

TP54

.01UF

C61

REDLED/AV

IRLED/AV

REDDC

.01UFC7

+5.7

3.32K

R67

LTC201U11A

LTC201U11B5

41

16

VCC

+

+

TP76

TP86

TP85

11

10

9

2

13

From U2 pin 3

IR

BUSTO CPU

Figure 9-15CPU Circuit

1N914CR10

2N3904

Q22

15KR156

15KR73RST

VCC

.1UF

C65

TP42

TP41

RESET GENERATION

100KR72

VCC

22PF

C8922PF

C88 10KR75

10KR76

10MHz

Y2

AD0

WRRD

BAT_VOLT

ALE

RAMEN

DISP_LATCH

PR_PRESENT

10K R131 VCC

LEDDIS

PWR_DOWN

PR_TACHPR_TEMP

RST

VCC

EATXDRXD

NMI

AD15AD14AD13AD12AD11AD10AD9AD8AD7AD6AD5AD4AD3AD2AD1

IR/RED

OFF/ON

PWM1

IRLED/AV

SAMPIR

SAMPRED

PWM0

PWM2

TP4

RST

10KR137

CPU

/ZERO

80C196KC

U31

53AD7/P3.7

54AD6/P3.6

55AD5/P3.5

56AD4/P3.4

57AD3/P3.3

58AD2/P3.2

59AD1/P3.1

60AD0/P3.0

61RD

62ALE/ADV

66XTAL2

16RESET

2EA

9ACH7/P0.7

8ACH6/P0.6

10ACH5/P0.5

11ACH4/P0.4

4ACH3/P0.3

7ACH2/P0.2

5ACH1/P0.1

6ACH0/P0.0

12ANGND

13VREF

14GND

15EXTINT/P2.2

67XTAL1

52AD8/P4.0

51AD9/P4.1

50AD10/P4.2

49AD11/P4.3

48AD12/P4.4

47AD13/P4.5

46AD14/P4.6

45AD15/P4.7

3NMI

65CLKOUT

64BUSWIDTH

63INST

43READY

41WRH/BHE

40WRL/WR

18TXD/P2.0

17RXD/P2.1

39P2.5/PWM0

37VPP

19P1.0

20P1.1

21P1.2

22P1.3/PWM1

23P1.4/PWM2

30P1.5/BREQ

31P1.6/HLDA

32P1.7/HOLD

35HSO3

34HSO2

29HSO1

28HSO0

27HSI3/HSO5

26HSI2/HSO4

25HSI1

24HSI0

38P2.7/T2CAPT

33P2.6/T2U-D

42T2RST/P2.4

44T2CLK/P2.3

VREF

PR_HEAD2PR_HEAD1

DISP_PHASEPR_STROBE

PHOTOI

REDLED/AV

RSENS

REDDC

IRACIRDCREDAC

AMB_LIGHT

9-39

9-41

Figure 9-20Output Port Circuit

150K

R154 150K

R153150K

R152 150K

R151150K

R150 150K

R149150K

R148

74HC574

U17

1OC

11CLK

12Q8

9D8

13Q7

8D7

14Q6

7D6

15Q5

6D5

16Q4

5D4

17Q3

4D3

18Q2

3D2

19Q1

2D1


150K

R123VCC

RTC_IO

PR_STROBEEXOUTEN

EX_OUT MSB

PR_DOT6PR_DOT5PR_DOT4PR_DOT3PR_DOT2PR_DOT1PR_DOT0

74HC574

U18

1OC

11CLK

12Q8

9D8

13Q7

8D7

14Q6

7D6

15Q5

6D5

16Q4

5D4

17Q3

4D3

18Q2

3D2

19Q1

2D1

TP82TEST

DISP_CLK

EXOUTEN

R132150K

EX_OUT LSB

RTC_CLKRTC_RSTPR_MOTOR

BEEP_2BEEP_1PR_MEAS

DISP_DATA


9-43

Figure 9-23Display Control Circuit

HDR 7

JP5

7654321

EL DRIVE

VCC

HDR 32

JP3

3231302928272625242322212019181716151413121110987654321

VCC

SI9530

U20

18DOUT

26SL

20OSCIN

21OSCOUT

22POL

23LATCH

25CLK

27DIN

28VPP

24VDD

19GND

29BP

30O32

31O31

32O30

33O29

34O28

35O27

36O26

37O25

38O24

39O23

40O22

41O21

42O20

43O19

44O18

1O17

2O16

3O15

4O14

5O13

6O12

7O11

8O10

9O9

10O8

11O7

12O6

13O5

14O4

15O3

16O2

17O1

TEST

TP80

VCC

VDISP

DISP_CLK

DISP_DATA

HDR 32

JP2

3231302928272625242322212019181716151413121110987654321

DISPLAY DRIVERSVCC

SI9530

U19

18DOUT

26SL

20OSCIN

21OSCOUT

22POL

23LATCH

25CLK

27DIN

28VPP

24VDD

19GND

29BP

30O32

31O31

32O30

33O29

34O28

35O27

36O26

37O25

38O24

39O23

40O22

41O21

42O20

43O19

44O18

1O17

2O16

3O15

4O14

5O13

6O12

7O11

8O10

9O9

10O8

11O7

12O6

13O5

14O4

15O3

16O2

17O1

DISP_DL

DISP_POL

6.19KR117

MMBT5551LQ21

MMBT5401LQ14

1%182R95

1%182R93

390PF

C87

390PF

C8310KR116

VDISP

+70V

VCC

12.1K

R114

475K

R115

4.75KR113

MMBT5551LQ12

2N3904Q13

TALIQ COLD SWITCH +70V

DISP_PHASE

DISP_DL

DISP_POL

74HC74

U34

7GND

8Q2

9Q2

6Q1

5Q1

14VCC

13RST2

11CLK2

12D2

10SET2

1RST1

3CLK1

2D1

4SET1

VCC

RST

DISPLAY PS CTRL

9-45

Figure 9-25Power Supply Circuit

+

22UFC82

120UH

L2

22UF

C90

LT1172

U26

5VIN

6E1

7VSW

8E2

3FB

2VC

1GND

MURS110CR31

MURS110CR16

MURS110CR30

5367A

CR25

R119

3.32K

R96

43V 10%5W

50V4.7UFC113

50V1UF

C112

0.1UF

C85

2N3904

Q8

TESTTP38

100V.1UFC124

1%390KR125

1%390KR126

1%14KR127

+70V

50V2.2UFC95

50V2.2UFC92

RAW10V

RAW-5V

RAW12V

130T3

CR20130T3

CR19

130T3

CR15

130T3CR14

22.1K

R120

22UFC125

31.6KR86

.47UF

C78

22UFC71

2N3906

Q9

2.2UFC96

22UFC79

.1UFC72

.1UF

C81

130T3

CR13

22UF

C119

22UF

C118

22UF

C70

LT1054CS

U23

14V +

13OSC

12VREF

11VOUT

6CAP -

5GND

4CAP +

3FB/SD

0.1UFC75 28.7K

R83

BATT PLUS

BATTERY INPUT

BATT GND

10KR155

SI9956DY

Q15 5

D2 6

D2

7D1

8D1

4G2

3S2

2G1

1S1

1.5A

F1

TEST

TP3

TEST

TP1

10V

TRANZORB

CR24

TO CENTER MOUNTING HOLE

22UFC117

22UFC116

22UFC74

0.1UFC73

VBAT

150

R134

120UH

L1

1M

R77

POWER SUPPLY

100KR82

LT1173

U22

5GND

6AO

7SET

8FB

4SW2

3SW1

2VIN

1ILIM

SI9405DY

Q17

5DRN

6DRN

7DRN

8DRN

4GATE

3SRC

2SRC

100PF

C76

100KR85

10K

R84

VCC

9-47

Figure 9-26Power Control Circuit

JP18

9

8

7

6

5

4

3

2

1

L11

PWR_DOWN

GO_SW

3.32K

R81

475KR110

0.1UF

C110

TESTTP73

TESTTP71

100PF

C123

0.1UFC67

VCON

1N914

CR11

TEST

TP84

LT1046

Q15

3

6 8

2

TESTTP83

0.1UFC68

PWR_ON

VCON

3.32KR79

15KR102

TEST

TP72

74HC74

U21

7GND

8Q2

9Q2

6Q1

5Q1

14VCC

13RST2

11CLK2

12D2

10SET2

1RST1

3CLK1

2D1

4SET1GO_BTN

VCC

.01UFC66

VCONVCON

150KR78

MAIN PCBTO: N-20

GO BTN

JP9

PIN 17

VBAT

9-49

Figure 9-32Printer Interface Circuit

1KR156

100pf

C127

130T3

CR28

VBAT

1A

F2

TESTTP31

0.1UFC115

VPRN

150K

R105

100PF

C122

100PF

C121

100PF

C120

L10VCC

VCC

TESTTP34

TESTTP33

TESTTP32

DD

ADV

TESTTP30

TESTTP29

PR_DOT4

PR_DOT3

PR_DOT2

PR_DOT1

PR_DOT0

PWR_ON

ON_OFF

PR_PRESENT

VPRN

PR_MOTOR

TESTTP28

TESTTP27

TESTTP26

TESTTP25

TESTTP24

TESTTP23

150K

R103150K

R104

L9

L8

VCC

1N914

CR29

3.32K

R147 1K

R141

150K

R142

2N3904

Q19

PR_MEAS

150K

R106

VCC

150K

R118

VCC

PR_HEAD2

VPRN

PR_HOME

PR_TACH

60.4KR145

TESTTP77

TESTTP36

TESTTP352N3904

Q20

TESTTP37

PR_DOT6

PR_DOT5

VPRN

VPRN

22 HDR

JP9

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

DOT4

TG

HM

TO PRINTER PCB

TEST

TP79

14.0KR143

1.24KR144

TESTTP78

59

R146

VPRN

LT1017CS

U36A

6

41

3 4

5

LT1017CS

U36B13

12

11

PR_PRESENT

VPRN

PR_HEAD1

ADV BTN

DD BTN

ON BTN

9-51

Figure 9-33Printer Flex circuit

0.01uFC6

S3

1K

R3

DAY/DATE BUTTON

DD

ADV

ON_OFF

PR_PRESENT

0.01uFC5

0.01uFC4

S2

1K

R2

ADVANCE BUTTON

S1

1K

R1

ON OFF BUTTON

3300UF

C3

SI9956DY

Q1

5D2

6D2

7D1

8D1

4G2

3S2

2G1

1S1PWR_ON

PR_DOT1

PR_DOT0

PR_MOTOR

PR_DOT6

PR_DOT5

PR_DOT4

PR_DOT3

PR_DOT2

LB1256

U1

9GND

12OUT6

13OUT5

14OUT4

15OUT3

16OUT2

17OUT1

18OUT0

11OUTM

10VCC

7IN6

6IN5

5IN4

4IN3

3IN2

2IN1

1IN0

8INM

DOT0DOT1DOT2DOT3DOT4DOT5DOT6DOT6

HEADER 8

JP11

87654321

PRINTER

MTP102-16

SEIKO

M+M-

HM

TG

HEADER 6

JP10

654321

VPRN

22 HDR

JP9

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

DOT4

TG

HM

TO N-20 AUX BOARD

9-53

Figure 9-34N-20PA Main PCB Schematic Diagram

3.32K

R20

OFF/ON

6R160

LF444

U1D

LTC201

8

88.7KR158

12VREF

390PFC40 R2

13

ACROSS U6-5V

TANT

SUPPLY

22UFC21

+12V 1M

R23

6

51.1K

.1%

3

414

14

15

7U6D

LT1097

4 81

-5V 16

.1UF

C35

8

7

VCC

-5V

VREF

2.0KR63

2 -5V

+12V

88.7K

U357 5

+12V .1%

R159

TP78

ACROSS U35SUPPLY

TANT.1UF

C124

ACROSS U11 16.1UF

100K

.12UF

1

1NF

C331312X1

X X0

Z

Y

Y1Y0

2

2N3906

9

Q6

U1C

220PFC126

VREF

91011

VSSZ1Z0

INHVEE

VDD CBA

3 5

6

U2

47.5K

R39

100K

R7

.12UF100K

14

15

OP490SO

U4D16

100K

R9

C16R6

TP81

OP490SO

10R8

11

12

U4C

.015UFC9

C13

SUPPLY-5V

3

LMC6044

11

2 1

3.32K

R29

1NFC28

U7A

+5.7

4

41

3.32K

R67

TP883

-5V

.1UF

C125

VREF

+12V

C12222UFC23

TANT

+12V VCC

5LTC201

U11BLTC201U11A2

1 REDLED/AV

.47UFC26

.1UF

+C27

TP55

REDAC

.01UF

C61C7.01UF

TP87 TP53

IRLED/AV

TP54

REDDC

SAMPRED

OFF/ONSAMPIR

PWM2

TP75

2.2MR68

33.2KR136

3.32K

R26

TP89

.068UF

100K100K 4

TP52

1NF

.47UF

82.5K

R24

R27

3.32KC25

C34 2N3906

5

6

LF444

U1B

7

-5V

.068UF

100K

R10

C17

.12UF 2

3

100K

OP490SO

31

U4A 1

R12

TP5182.5K

VREF

C24.47UF

R254053

Q7 220PFC127

VREF

LF444

10 8

+12V

.068UF

C18R11

C15C14

12.1K U7C

.12UFC19 15K

R41

TP85LMC6044

8

47.5KR40

9 10 11 6

3 5

9

1N914CR3

1N914

CR1 VREF

LTC20110

R22

11U11C

VREF34.8K

R28

3.32K

R60

100K

1 2

13 12

R30

.1UF

C58

VCC4053

INH

CBA VEE

VDD

Z1Z0

VSS

7

16

8

TP57

TP56

X1

Y1Y0

Z

Y

U3

X0 X

4

15

14

PWM1

.01UFC56

.01UF

VTB8442BD8

C63

MMBTA13LQ8

LIGHT SENSORVCC

VCC

TP72

3.57KR135

2N3906Q25

LED DRIVE

DB9F

P1

L-8

MMBTA56

.1UF

C55

100PF

11

TP45 4

100PF

C116

TP47

L5

L3

2

1 6

7 3 8

L4

100PF

C117 C118

TP44SENSOR

L2L1

INPUT

9 5

LTC201U6C

10

VREF

3.32K

-5V

LF444

Q4MMBTA56

10K

TP50

TP46

R64

Q1

MMBTA06

R51

10KR48

10K

VREF

VCC

Q3

R4610K

.047UFC22

511KR157

2

R45

LTC201U6B

15

61

14

4

18PFC1

9 11

3.32K

182K

R58

R1

U1A

1

+12V

R17 1M

280KR19

3 .047UFC59

TP49

LTC201

3U6A

2

1

.068UF

VCC

14 12

VEE

VSS

VDD

10 11

9 B

4053

C

AINH 6

13

1

Z1Z0

Y1

3 5

Y0

X1X0

2

8

16

7

.1UF

VCC

C53

4Z

15Y

X

LT1013

U9A

7

VREF

U106 R42

.1UFC36

.022UF

C39

2

8

1

100K

R53

4.7PF

20KR43

182KR50

TP83

280K

C60

8

1N914

C20CR4

1N914

VREF

TP90

CR2

VREF

12.1K

R31

LTC201

.015UFC29

6

7

U11D

OP490SO

U4B 6

5 7

R66.01UF

R37

1NF

LMC6044

U7B

6

C32

5 7

3.32K.01UFC57

3.32K

3.32K

R61

R33

100K

R36

C111C8

.47UF

.01UF

C30

.1UF+C31

/ZERO

TP59

TP58

IRAC

REDLED/AV

3.32K

R21IRDC

PWM0OFF/ON

VREF

R52

1. ALL RESISTORS 1/8W 1% UNLESS OTHERWISE SPECIFIED.

R124

NOTES:

TO CENTER MTG. HOLE

.1UF

RAW-5V

221

RAW12V221

R122

R121

TP62

C94 22UFC93

2N3904

TP61

-5V

.1UFC80 22UF

C91

+12V

VREF

22UFC95

RAW10V182

R123

100PF

.01UFC5

6.04K0.1%

R18

RSENS

TP48

TP60

2N3904Q23

TRIMVOUT

10K

R161

Q24

4 2

LT1021

GND

U32

VIN

+5.7

5 6

.1UFC6

1

R546.8

VREF

MMBTA06

22.1K

Q2

10KR47

1N914

.1UF.1UF.1UF

TP64

GNDTP70

C1222UF

22UFC11

TP63

IR/RED

2N3904Q5 TP77

C52C50 C51

100K

R162

100K

22UFC48

VCC

1N914CR18

.022UF

C38

100K

R49

22PF

CR12

C123

.1UFC37

20KR44

.1UF.1UF.1UF.1UF.1UF.1UF

C105C10222UFC49 C106 C107

15KR5

TP86

C109C108

34.8K 12

TP79

LMC6044

15.8K

R56

14C119 VREF TP84 13

U7D

R70SENSE1%

47.5K .01UFC62

VBAT

VOLTAGEBATTERY

TP73

BAT_VOLT

15.8K 1%

R69

RSENS

LEDDIS

LT1013

TP80

4

3

40.2K

5

U9B

OFF/ON

IR/RED

PHOTOI

R57 TP76

RXD

GND

Q2Q2

TXD

TALIQ PS CTRL

CPU

EXTINT/P2.2

AD0


60

57 58 59

53 54 55 56

PR_TACHACH7/P0.7

15


RDWR

ALE

52 51 50 49 48 47 46 45

RDALE/ADV

GND

WRL/WR

VPP 62 61

41 40

14

37VCC

BAT_VOLTPR_TEMP

RSENS

REDDCREDAC

AMB_LIGHT

IRACIRDC

6

ACH6/P0.6ACH5/P0.5ACH4/P0.4ACH3/P0.3ACH2/P0.2ACH1/P0.1ACH0/P0.0

11 10

9 8

4 7 5

U31

ANGNDVREF

VREF

12 13

BUSWIDTH

R75

67XTAL1XTAL2RESET

CLKOUT

TXD/P2.0RXD/P2.1

EA

6616 2

NMI 365

1817

10KR76

10K

RST

TXDEA

RXD

NMI

TP65

TP4

10KR128

TP66

SAMPIR34

10K

P1.3/PWM1

READYINST 64

6343

P1.0P1.1P1.2

192021

P2.5/PWM0

P1.4/PWM2P1.5/BREQP1.6/HLDAP1.7/HOLD 31

222330

HSO3HSO2

3932

35

RAMEN

DISP_LATCH

R131

LEDDISIR/RED

VCC

PR_PRESENT

PWR_DOWNIRLED/AV

PWM1PWM2

PWM0

33

HSI3/HSO5HSI2/HSO4

P2.7/T2CAPTP2.6/T2U-D

26

HSO0HSO1 29

2827

HSI1HSI0 25

2438

T2RST/P2.4T2CLK/P2.3 42

44

REDLED/AV

OFF/ONSAMPRED

DISP_PHASEPR_STROBE

/ZEROPHOTOI

PR_HEAD2PR_HEAD1

VCC

RST

SET2

74HC74

VCC

RST2CLK2D2

14

13 11 12

U34

RST1CLK1D1SET1

3

10

1

2 4

Q1Q1

10KR137

DIGITAL SECTION

GO BUTTON

PR_PRESENT 7

4 HDR

JP1

4

100PF

C121C120

100PF

L7

BEADL6

3BEAD

VCC

21

PORT

SERIAL DATA

RAW-5V

RAW12V

DISP_POL

DISP_DL

RAW10V

PWR_DOWN

DISP_PHASE

DISP_DL

7

8 9

DISP_POL 6 5

20 HDR

20

19

18

17

16

15

VBAT

VCC

14

13

12

11

10

9

8

PR_STROBE

PR_HEAD2

PR_HEAD1

PR_TACH

GO_SW

221

R80

S2

AUX PCBJP8

6

5

4

3

2

1

TO: N-20

TEMP SENSOR

7TP41Q3D3 D2A2

ROMEN

A15A14A13A12A11A10A9A8A7A6A5A4A3A2

A0A1

TP11

LM35

3

TEMP

GND

PR_TEMP 2

C115.1uF

U5

VCC 1 VCC

TP19

TP22TP21 RD

TP20

TP15

TP18TP17TP16

TP14TP13TP12

AD8 19Q1

2D1 A8

10KR109

74HC573TP40

ALE 1 11


6

9 8 7

5 4 3

OCC

TP7

TP10

TP8TP9

TP5TP6

D8D7D6D5

Q8Q7Q6Q5

D4D3D2

Q4Q3Q2

15 A12

121314

A15A14A13

161718

A11A10A9

10KR108

TP39

ALE

AD7

1 11

9AD6AD5AD4AD3

8 7 6 5

OC

U33

74HC573

Q7D7

C

D8 Q8

D6D5D4

Q6Q5Q4

12 A713141516

A6A5A4A3

AD6A7 15 30

4 5 6 7 8 9

14

27C1024L

RD

VCCVCC

ROMEN

A15A14A13A12A11A10A9A8

O13A13

CE

43 2 22

PGMVPPOE

3

41 40

A15A14

O15O14

A9

39 38 37 36

A12A11A10

35 32 31

A8A7A6

O9

O12

O10O11

O8O7O6

1011

A14

A11A15

AD15AD14AD13AD12AD11AD10

AD7

AD9AD8

A14A15

A13A12

A10

WRRD

20

64K X 16 EPROM

VCC

TP43

A3

A6A5A4

A2A1

26

29 28 27

A5A4A3A2

25 24

U15

A1A0

19

O5O4O3O2

161718

O1O0 21

RAMEN

WRRD

A12A11A10A9A8A7A6A5A4A3

A10

CS1

22 27 26

OEWECS2

20

2 23

A12A11

A6

21 24 25 3

A9A8A7

4 5 6 7

A5A4A3

D6D7 19

D5D4D3

18171615

AD2

AD5AD4AD3

AD1AD0

10KR133

AD7AD6AD5AD4AD3

2N3904

Q22

RST

R134

VCC

15 1

12

DC00-DFFF

74HC10

TP71

U30B 3

5 4 6

74HC10

10K

U30C

74HC10

11 10 9

74HC138

G2BG2AG1

5 4 6

3C

2 BA

Y7

U30A

13 2 1

1011121314

Y3

Y6Y5Y4

Y2Y1Y0

7 9

ROMEN0000-DBFF

8

TP74

AUX PCB

RAMENE000-FFFF

AD10

AD9

AD8

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

U28

ADDRESS DECODING

1N914CR10

TP42

475KR156

475K

.1UF

R73

15

TO: N-20

20 HDR

20

19

18

17

16

EXINEN

EXOUTEN

14

13

12

11

10

9

8

RESET GENERATION

ADDRESS DEMUX

AD2AD1AD0

4 3 2

U13

D2D1

Q2Q1

171819

A2A1A0

8K X 8 SRAM

A2A1A0

22PF

U14

8 9 10

A1A0

D1D0

131211

10MHzC8922PF

C88

Y2

AD2AD1AD0

100KR72

VCC

AD15

AD14

AD13

AD12

AD11

C65

VCC

JP7

6

5

4

3

2

1

SpO2 ANALOG

9-55

Figure 9-35N-20PA Auxiliary PCB Schematic Diagram

VCC

R8410K

R85100K

C76100PF

SRC 2

SRC 3

GATE 4

DRN 8

DRN 7

DRN 6

DRN 5

Q17

SI9405DY

ILIM 1

VIN 2

SW1 3

SW2 4

FB 8

SET 7

AO 6

GND 5

U22

LT1173

R82100K

POWER SUPPLYR77

1M

L1

120UH

R134

150

VBAT

C73.1UF

C7422UF

C11622UF

C11722UF

TO CENTER MOUNTING HOLE

CR24TRANZORB

10V

VCC

TP1

TEST

TP3

TEST

F1

1.5A

S1 1 G1 2

S2 3 G2 4

D1 8D1 7

D2 6D2 5

Q15

SI9956DY

R15510K

BATT GND

BATTERY INPUT

BATT PLUS

VRECHARGE

TO: N-20

MAIN PCBR78150K

VCON VCON

C66.01UF

VCC

GO_BTNSET1

4

D1 2

CLK1 3

RST1 1

SET2 10

D2 12

CLK2 11

RST2 13

VCC 14

Q1 5

Q1 6

Q2 9

Q2 8

GND 7

U21

74HC74

R100

15K

TP2

TESTR101150K

TP72

TESTR102

15K

R793.32K

CR271N914

VCON

PWR_ON

C68.1UF

BAT_TYPE

TP83TEST

JP9PIN 17

TP84

TEST

R8328.7KC75

.1UF

FB/SD 3

CAP + 4

GND 5

CAP - 6VOUT 11

VREF 12

OSC 13

V + 14

U23

LT1054CS

C70

22UF

C118

22UF

C119

22UF

C81

.1UF

C72.1UF

C7922UF

C962.2UF

C7122UF

C78

.47UF

R8631.6K

C12522UF

R120

22.1K

RAW12V

RAW-5V

RAW10V

C922.2UF50V

C952.2UF50V

+70V

R12714K1%

R126390K1%

R125390K1%

C124.1UF100V

TP38TEST

C85.1UF

C1121UF50V

C1134.7UF50V

5W43V 10%

R96

3.32K

R119

22.1K

CR255367A

CR30MURS110

GND 1

2

FB 3

E2 8

VSW 7

E1 6

VIN 5

U26

LT1172

C90

22UF

L2120UH

C8222UF

VCC

R71150K

CHECK BATTERY

O1 17

O2 16

O315

O4 14

O513

O612

O711

O810

O9 9

O10 8

O11 7

O12 6

O13 5

O14 4

O15 3

O16 2

O17 1

O18 44

O19 43

O2042

O21 41

O2240

O23 39

O24 38

O2537

O2636

O2735

O2834

O2933

O3032

O3131

O3230

BP29

GND 19

VDD 24

VPP 28

DIN 27

CLK 25

LATCH 23

POL 22

OSCOUT 21

OSCIN 20

SL 26

DOUT 18

U19

SI9530

VCCTALIQ DRIVERS

VCON

C67.1UF

C123

100PF

TP71TEST

TP73TEST

C110

.1UF

1234567891011121314151617181920212223242526272829303132

JP2

HDR 32

R110475K

R81

3.32K

GO_SW

PR_TACH

PR_HEAD1

PR_HEAD2

PR_STROBE

DISP_PHASE

PWR_DOWN

PR_PRESENT

DISP_DL

DISP_POL

L11

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

JP18

20 HDR

DISP_DATA

DISP_CLK

VCC

AD15

VBAT

RAW12V

RAW-5V

RAW10V

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

JP17

20 HDR

VDISP

VCC

TP80

TEST


VCC

GO_BTN

BAT_BTN

ON_OFF_BTNDD_BTNADV_BTNPR_HOMEBAT_TYPE

R74

1KC64.01UF

RTC_IO

EX_IN INPUT PORT

SW1

L12

C126

100PF

TP88

TEST

D1 2

Q1 19

D2 3Q2 18

D3 4Q3 17

D4 5

Q4 16

D5 6Q5 15

D6 7

Q6 14

D7 8Q7 13

D8 9Q8 12

C11

OC 1

U16

74HC573

PR_HEAD1

VPRN

PR_PRESENT

TP81

TEST

11

12 13

U36B

LT1017CS

5

4 3

14

6

U36A

LT1017CS

DISP_PHASE

VPRN

R146

59

+70VTALIQ COLD SWITCH

Q132N3904

Q12MMBT5551L

R1134.75K

R115

475K

R11412.1K

TP78TEST

R1441.24K

R14314.0K

TP79TEST

VCC

+70V

VDISP

R11610K

C83390PF

C87390PF

R93182

1%

R95182

1%

Q14MMBT5401L

Q21MMBT5551L

R1176.19K

TO PRINTER PCB

HM

TG

DOT4

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

JP9

22 HDR

VPRN

VPRN

PR_DOT5

PR_DOT6

TP37TEST

Q202N3904

TP35TEST

TP36TEST

TP77TEST

R14560.4K

PR_TACH

PR_HOME

VPRN

PR_HEAD2

VCC

R118150K

VCC

R106150K

PR_MEAS

Q19

2N3904

R142

150K

R141

1KR147

3.32K

BZ1

AT17


DISP_DATA

PR_MEASBEEP_1BEEP_2

PR_MOTORRTC_RSTRTC_CLK

EX_OUT LSB

R132150K

EXOUTEN

EXINEN

DISP_CLK

TP82TEST

D1 2

Q119

D2 3 Q2 18

D3 4 Q3 17

D4 5

Q416

D5 6 Q5 15

D6 7

Q614

D7 8

Q713

D8 9

Q812

CLK 11

OC 1

U18

74HC574

O1 17

O2 16

O315

O4 14

O513

O612

O711

O810

O9 9

O10 8

O11 7

O12 6

O13 5

O14 4

O15 3

O16 2

O17 1

O18 44

O19 43

O2042

O21 41

O2240

O23 39

O24 38

O2537

O2636

O2735

O2834

O2933

O3032

O3131

O3230

BP29

GND 19

VDD 24

VPP 28

DIN 27

CLK 25

LATCH 23

POL 22

OSCOUT 21

OSCIN 20

SL 26

DOUT 18

U20

SI9530

VCC 1234567891011121314151617181920212223242526272829303132

JP3

HDR 32

AD3

AD4

AD5

AD6

AD7

AD8

AD9

AD10

AD11

AD12

AD13

AD14

AD0

AD1

AD2

EXINEN

EXOUTEN

TO: N-20

MAIN PCB

VCC

VCC REAL TIME CLOCK

PR_DOT0PR_DOT1PR_DOT2PR_DOT3PR_DOT4PR_DOT5PR_DOT6

EX_OUT MSB

EXOUTENPR_STROBE

RTC_IO

VCCR123

150K


D1 2 Q1 19

D2 3

Q218

D3 4 Q3 17

D4 5

Q416

D5 6 Q5 15

D6 7 Q6 14

D7 8

Q713

D8 9

Q812

CLK 11

OC 1

U17

74HC574

R148

R149

150KR150

150K R151

150KR152

150K

BEEPER

TP74

TESTTP75TEST

VCC

L8

L9

R104

150K R103

150K

TP23TEST

TP24TEST

TP25TEST

TP26TEST

TP27TEST

TP28TEST

PR_MOTOR

VPRN

PR_PRESENT

ON_OFF

PWR_ON

PR_DOT0

PR_DOT1

PR_DOT2

PR_DOT3

PR_DOT4

TP29TEST

TP30TEST

ADV

DD

TP32TEST

TP33TEST

TP34TEST

VCC

VCCL10

C120

100PF

C121

100PF

C122

100PF

R105

150K

VPRN

C115.1UF

TP31TEST

F2

1A

RTC_CLKRTC_IO

RTC_RST

VBAT

R153

150KR154

150K

TP85

TEST

TP87

TEST

TP86

TEST

BT13V

Y1

32.768KHz

C114

.1uF

TP76

TESTSCLK

14

I/O12

RST 9

VCC 16

X1 3

X2 5

GND 8

U29

DS1202S

CR23

1N914

EL DRIVE

VCC

C99

.1UF

C100

.1UF

C101

.1UFC4922UF

1234567

JP5

HDR 7

C97

.1UF

C98

.1UF

DIGITAL IC'S BYPASS CAPS

C127

100pf

R156 1K

3.32KR163

+

VC

150K

LT1046

3

6

8

2

9-57

Figure 9-36N-20PA Flex Circuit Schematic Diagram

TO N-20 POWER SUPPLY BOARD

HM

TG

DOT4

JP9 VPRN

PR_DOT2

PR_DOT3

PR_DOT4

PR_DOT5

PR_DOT6

PR_MOTOR

PR_DOT0

PR_DOT1

10

11

12

13

14

15

16

17

18

19

20

21

22

1

2

3

4

5

6

7

8

9

22 HDR

ON OFF BUTTONR1

1K

S1

ADVANCE BUTTONR2

1K

S2

C40.01uF

C50.01uF

DAY/DATE BUTTONR3

1K

S3

C60.01uF

S1 1

G1 2

S2 3

G2 4

D1 8

D1 7

D2 6

D2 5

Q1

SI9956DY

PWR_ON

PR_PRESENT

ON_OFF

ADV

DD

INMIN0IN1IN2IN3IN4IN5IN6

VCC

OUTMOUT0OUT1OUT2OUT3OUT4OUT5OUT6

GND

U1

LB1256

C3

3300UF

8 1 2 3 4 5 6 7

10

1118171615141312

9

12345678

JP11

HEADER 8

DOT6DOT6DOT5DOT4DOT3DOT2DOT1DOT0

TG

HM

M-M+ 1

23456

JP10

HEADER 6SEIKO

MTP102-16

PRINTER

nellcor oximetro portatil servicio

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