iso122sensor de tension
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Precision Lowest CostISOLATION AMPLIFIER
FEATURES
100% TESTED FOR HIGH-VOLTAGEBREAKDOWN
RATED 1500Vrms
HIGH IMR: 140dB at 60Hz
BIPOLAR OPERATION: VO
= 10V 16-PIN PLASTIC DIP AND 28-LEAD SOIC
EASE OF USE: Fixed Unity GainConfiguration
0.020% max NONLINEARITY
4.5V to 18V SUPPLY RANGE
APPLICATIONS
INDUSTRIAL PROCESS CONTROL:Transducer Isolator, Isolator for Thermo-
couples, RTDs, Pressure Bridges, andFlow Meters, 4mA to 20mA Loop Isolation
GROUND LOOP ELIMINATION
MOTOR AND SCR CONTROL
POWER MONITORING
PC-BASED DATA ACQUISITION
TEST EQUIPMENT
VOUT
VIN
+VS1
ISO122
DESCRIPTIONThe ISO122 is a precision isolation amplifier incor-
porating a novel duty cycle modulation-demodulation
technique. The signal is transmitted digitally across
a 2pF differential capacitive barrier. With digital modu-
lation the barrier characteristics do not affect signal
integrity, resulting in excellent reliability and good high
frequency transient immunity across the barrier. Both
barrier capacitors are imbedded in the plastic body of
the package.
The ISO122 is easy to use. No external components
are required for operation. The key specifications are
0.020% max nonlinearity, 50kHz signal bandwidth,
and 200V/C VOS
drift. A power supply range of
4.5V to 18V and quiescent currents of 5.0mA onV
S1and 5.5mA on V
S2make these amplifiers ideal
for a wide range of applications.
The ISO122 is available in 16-pin plastic DIP and 28-
lead plastic surface mount packages.
VS1
Gnd
+VS2
VS2
Gnd
1989 Burr-Brown Corporation PDS-857F Printed in U.S.A. November, 1993
International Airport Industrial Park Mailing Address: PO Box 11400 Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd. Tucson, AZ 85706
Tel: (520) 746-1111 Twx: 910-952-1111 Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
SBOS160
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ISO122
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the users own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
SPECIFICATIONSAt T
A= +25C , V
S1= V
S2= 15V, and R
L= 2kunless otherwise noted.
ISO122P/U ISO122JP/JU
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
ISOLATION
Voltage Rated Continuous AC 60Hz 1500 * VAC
100% Test (1) 1s, 5pc PD 2400 * VAC
Isolation Mode Rejection 60Hz 140 * dB
Barrier Impedance 1014 || 2 * || pFLeakage Current at 60Hz V
ISO= 240Vrms 0.18 0.5 * * Arms
GAIN VO= 10V
Nominal Gain 1 * V/V
Gain Error 0.05 0.50 * * %FSR Gain vs Temperature 10 * ppm/ C Nonlinearity(2) 0.016 0.020 0.025 0.050 %FSR
INPUT OFFSET VOLTAGE
Initial Offset 20 50 * * mV vs Temperature 200 * V/C vs Supply 2 * mV/VNoise 4 * V/Hz
INPUT
Voltage Range 10 12.5 * * VResistance 200 * k
OUTPUT
Voltage Range 10 12.5 * * VCurrent Drive 5 15 * * mACapacitive Load Drive 0.1 * FRipple Voltage(3) 20 * mVp-p
FREQUENCY RESPONSE
Small Signal Bandwidth 50 * kHz
Slew Rate 2 * V/ sSettling Time V
O= 10V
0.1% 50 * s 0.01% 350 * sOverload Recover Time 150 * s
POWER SUPPLIES
Rated Voltage 15 * VVoltage Range 4.5 18 * * VQuiescent Current: V
S1 5.0 7.0 * * mA
VS2 5.5 7.0 * * mATEMPERATURE RANGE
Specification 25 +85 * * COperating 25 +85 * * CStorage 40 +85 * * C
JA100 * C/W
JC
65 * C/W
* Specification same as ISO122P/U.
NOTES: (1) Tested at 1.6 X rated, fail on 5pC partial discharge. (2) Nonlinearity is the peak deviation of the output voltage from the best-fit straight line. It is expressed
as the ratio of deviation to FSR. (3) Ripple frequency is at carrier frequency (500kHz).
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ISO122
Top View P Package
1
2
7
8
16
15
9
Gnd
VIN
VOUT
VS1
+VS1
10
+VS2
Gnd
VS2
Top ViewU Package
1
2
28
27
Gnd
VIN
VOUT
VS1
+VS1
+VS2
Gnd
VS2
16
15
13
14
CONNECTION DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Supply Voltage ...................................................................................18VV
IN......................................................................................................100V
Continuous Isolation Voltage ..................................................... 1500Vrms
Junction Temperature .................................................................... +150CStorage Temperature ....................................................................... +85CLead Temperature (soldering, 10s) ................................................ +300C
Output Short to Common ......................................................... Continuous
PACKAGE INFORMATION(1)
PACKAGE DRAWING
MODEL PACKAGE NUMBER
ISO122P 16-Pin Plastic DIP 238
ISO122JP 16-Pin Plastic DIP 238
ISO122U 28-Pin Plastic SOIC 217-1
ISO122JU 28-Pin Plastic SOIC 217-1
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix D of Burr-Brown IC Data Book.
NONLINEARITY
MODEL PACKAGE MAX %FSR
ISO122P Plastic DIP 0.020ISO122JP Plastic DIP 0.050ISO122U Plastic SOIC 0.020ISO122JU Plastic SOIC 0.050
ORDERING INFORMATION
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ISO122
+10
0
10
0
OutputVoltage(V)
500
Time (s)
SINE RESPONSE
(f = 2kHz)
1000
Time (s)
+10
0
10
0
OutputVoltage(V)
10050
SINE RESPONSE
(f = 20kHz)
Time (s)
+10
0
10
0
OutputVoltage(V)
STEP RESPONSE
10050
Time (s)
+10
0
10
0
OutputVoltage(V)
STEP RESPONSE
500 1000
TYPICAL PERFORMANCE CURVEST
A= +25C, V
S= 15V unless otherwise noted.
100
0
100M10M
ISOLATION VOLTAGE
vs FREQUENCY
Typical
Performance
Frequency (Hz)
100k10k
Max DC Rating
1k
PeakIso
lationVoltage
Degraded
Performance
100 1k 1M
2.1k
IMR vs FREQUENCY
1M1
Frequency (Hz)
160
140
120
100
80
60
40
10 100 100k10k1k
IMR
(dB)
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ISO122
TYPICAL PERFORMANCE CURVEST
A= +25C, V
S= 15V unless otherwise noted.
PSRR vs FREQUENCY
60
40
20
0
Frequency (Hz)
1 10 100 1k 10k 100k 1M
54
PSRR
(dB)
VS1
, VS2
+VS1
, +VS2
Frequency (Hz)
100mA
10mA
1mA
100A
10A
1A
0.1A
1 10 100 1k 10k 100k 1M
ISOLATION LEAKAGE CURRENT
vs FREQUENCY
LeakageCurrent(rms)
1500Vrms
240Vrms
Input Frequency
0 500kHz 1MHz 1.5MHz
0
10
20
30
40
250
200
150
100
50
VOUT
/V
INdBm
SIGNAL RESPONSE TO
INPUTS GREATER THAN 250kHz
FrequencyOut
100kHzVOUT
/VIN Freq
Out
(NOTE: Shaded area shows aliasing frequencies that cannot
be removed by a low-pass filter at the output.)
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ISO122
THEORY OF OPERATIONThe ISO122 isolation amplifier uses an input and an output
section galvanically isolated by matched 1pF isolating ca-
pacitors built into the plastic package. The input is duty-
cycle modulated and transmitted digitally across the barrier.
The output section receives the modulated signal, converts it
back to an analog voltage and removes the ripple component
inherent in the demodulation. Input and output sections arefabricated, then laser trimmed for exceptional circuitry match-
ing common to both input and output sections. The sections
are then mounted on opposite ends of the package with the
isolating capacitors mounted between the two sections. The
transistor count of the ISO122 is 250 transistors.
MODULATOR
An input amplifier (A1, Figure 1) integrates the difference
between the input current (VIN/200k) and a switched
100A current source. This current source is implementedby a switchable 200A source and a fixed 100A currentsink. To understand the basic operation of the modulator,
assume that VIN = 0.0V. The integrator will ramp in onedirection until the comparator threshold is exceeded. The
comparator and sense amp will force the current source to
switch; the resultant signal is a triangular waveform with a
50% duty cycle. The internal oscillator forces the current
source to switch at 500kHz. The resultant capacitor drive is
a complementary duty-cycle modulation square wave.
DEMODULATOR
The sense amplifier detects the signal transitions across the
capacitive barrier and drives a switched current source into
integrator A2. The output stage balances the duty-cycle
modulated current against the feedback current through the
200kfeedback resistor, resulting in an average value at the
VOUT
pin equal to VIN
. The sample and hold amplifiers in the
output feedback loop serve to remove undesired ripple
voltages inherent in the demodulation process.
BASIC OPERATION
SIGNAL AND SUPPLY CONNECTIONSEach power supply pin should be bypassed with 1F tanta-lum capacitors located as close to the amplifier as possible.
The internal frequency of the modulator/demodulator is set
at 500kHz by an internal oscillator. Therefore, if it is desired
to minimize any feedthrough noise (beat frequencies) from
a DC/DC converter, use a filter on the supplies (see Figure4). ISO122 output has a 500kHz ripple of 20mV, which can
be removed with a simple two pole low-pass filter with a
100kHz cutoff using a low cost op amp. See Figure 4.
The input to the modulator is a current (set by the 200kintegrator input resistor) that makes it possible to have an
input voltage greater than the input supplies, as long as the
output supply is at least 15V. It is therefore possible whenusing an unregulated DC/DC converter to minimize PSR
related output errors with 5V voltage regulators on theisolated side and still get the full 10V input and outputswing. An example of this application is shown in Figure
10.
CARRIER FREQUENCY CONSIDERATIONS
The ISO122 amplifier transmits the signal across the isola-
tion barrier by a 500kHz duty cycle modulation technique.
For input signals having frequencies below 250kHz, this
system works like any linear amplifier. But for frequencies
above 250kHz, the behavior is similar to that of a sampling
amplifier. The signal response to inputs greater than 250kHz
1pF
200A
100A
200k
Isolation Barrier
1pF
1pF
200A
100A200kV
IN
+
Osc
Gnd 1 VS1+VS1
VOUT
S/H
G = 6
S/H
G = 1
Gnd 2+VS2 VS2
+A2
SenseSense
FIGURE 1. Block Diagram.
A1
150pF 150pF
1pF
| |
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ISO122
performance curve shows this behavior graphically; at input
frequencies above 250kHz the device generates an output
signal component of reduced magnitude at a frequency
below 250kHz. This is the aliasing effect of sampling at
frequencies less than 2 times the signal frequency (the
Nyquist frequency). Note that at the carrier frequency and its
harmonics, both the frequency and amplitude of the aliasing
go to zero.
ISOLATION MODE VOLTAGE INDUCED ERRORS
IMV can induce errors at the output as indicated by the plots
of IMV vs Frequency. It should be noted that if the IMV
frequency exceeds 250kHz, the output also will display
spurious outputs (aliasing), in a manner similar to that for
VIN
> 250kHz and the amplifier response will be identical to
that shown in the Signal Response to Inputs Greater Than
250kHz performance curve. This occurs because IMV-
induced errors behave like input-referred error signals. To
predict the total error, divide the isolation voltage by the
IMR shown in the IMR vs Frequency curve and compute the
amplifier response to this input-referred error signal from
the data given in the Signal Response to Inputs Greater than250kHz performance curve. For example, if a 800kHz
1000Vrms IMR is present, then a total of [(60dB) +
(30dB)] x (1000V) = 32mV error signal at 200kHz plus a
1V, 800kHz error signal will be present at the output.
HIGH IMV dV/dt ERRORS
As the IMV frequency increases and the dV/dt exceeds
1000V/s, the sense amp may start to false trigger, and theoutput will display spurious errors. The common mode
current being sent across the barrier by the high slew rate is
the cause of the false triggering of the sense amplifier.
Lowering the power supply voltages below 15V maydecrease the dV/dt to 500V/s for typical performance.
Isolation Barrier
VIN
1F
+VS2
VS1+V
S1
1F1F
Gnd
VS2
1F
VOUT
Gnd
VS1
VS2
FIGURE 2. Basic Signal and Power Connections.
HIGH VOLTAGE TESTING
Burr-Brown Corporation has adopted a partial discharge test
criterion that conforms to the German VDE0884 Optocou-
pler Standards. This method requires the measurement of
minute current pulses (
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ISO122
FIGURE 4. OptionalFilter to Minimize Power Supply Feedthrough Noise; Output Filter to Remove 500kHz Carrier Ripple.
For more information concerning output filter refer to AB-023.
Isolation Barrier
VS1
10H
10H 10H
10H
1F
1F 1F 1F
1F
1F 1F 1F
VS1
VIN ISO122
+VS1
+VS2
VS2
Gnd
13k
13k
100pF
+
6
VOUT
= VIN
Gnd
4700pF
385
Charge/Discharge
Control
10k
10k
25k
25k
7
V+V
25k
25k+
INA105
1
3 V = e50 2
5
6
V = e1
2
Control
SectionMultiplex
er
+V
ISO122P
10k
10k
15
9
7
8
V
+V
ISO122P
9
7
8
V
4e
49=12V
e50
=12V
e1= 12V
e2= 12V
FIGURE 5. Battery Monitor for a 600V Battery Power System. (Derives Input Power from the Battery.)
10
VS2
This Section Repeated 49 Times.
10
1
2
16
15
16
2
1
OPA602
2
3
2
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ISO122
10.0V
Thermocouple
REF
102
27kR
1
R4
+In
In
15V
2
14
13
1R
G
12
10
3
5
4
11
R5
R3
R2
IsothermalBlock with1N4148 (1)
Ground Loop Through Conduit
100
Zero Adj
R6
50100
+15V
+15V 15V +15V 15V
1
2
9
8
16
15 10 7V
OUT
ISO122P
FIGURE 6. Thermocouple Amplifier with Ground Loop Elimination, Cold Junction Compensation, and Up-scale Burn-out.
SEEBACK
ISA COEFFICIENT R2
R4
TYPE MATERIAL (V/C) (R3= 100) (R
5+ R
6= 100)
Chromel
E Constantan 58.5 3.48k 56.2kIron
J Constantan 50.2 4.12k 64.9kChromel
K Alumel 39.4 5.23k 80.6kCopper
T Constantan 38.0 5.49k 84.5k
NOTE: (1) 2.1mV/C at 2.00A.
1M
INA101
2
6 4
+15V
0.0
1
F
6
5
RTD
(PT100)
1mA1mA
2mA
R2= 2.5k
V
0V-5V
+V
Gnd
VS= 15V
on PWS740
4-20mA
ISO122P3
214
9
8
2
11
8
74
3
VOUT
10
7
12
4
10
XTR101
+VS=15V
on PWS740
R1= 100
10
11
5, 13
15
16
15
16
1
FIGURE 7. Isolated 4-20mA Instrument Loop. (RTD shown.)
RS
RCV420
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ISO122
FIGURE 8. Isolated Power Line Monitor.
MPY100
X
Y
(V2)
PL= V
2(R
D1+ R
D2)
RS
RD2
XY
10
(V1)
10k
2
36
0.01FISO122P
V
(V3)
VL= V
3(R
D1+ R
D2)
RD2
+VISO122P
2kIL= V
1
10RS
0.1F
2k
+V
9715
16
8
Load IL
RD2
RD1
VL
RS
0.3F
0.3F
PWS740-3
63
1 4
2 13
46 5
PWS740-2
To PWS740-1
0.3F
0.3F
97
8
15
16
41
PWS740-3
3 6
PWS740-2
To PWS740-1
13 2
456
21
12
10
10
V
OPA602
+
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ISO122
FIGURE 9. Three-Port, Low-Cost, Four-Channel Isolated, Data Acquisition System.
+V
Channel 2
(Same as Channel 1.)
PWS740-1
4 65
33
4 4
0.3F
ISO122P
0.3F
0.3F
64
1 1
66
16
15 7
0.3F
Channel 1
1
Channel 4
(Same as Channel 1.)
Channel 3
(Same as Channel 1.)
98
2
VIN
VOUT
123123
20H
PWS740-2 PWS740-2
50.3F
10F
6
3
4
8
5
10
PWS740-3 PWS740-3
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ISO122
+15V
9
7
8
10
VIN
, up to
10V Swing
216
1 15
0.1F0.1F
0.33F 0.33F4
PWS7403
VOUT
To PWS7402,1
NOTE: The input supplies can be subregulated to 5V to reducePSR related errors without reducing the 10V input range.
12
3
1
2
3MC78L05
+5V
Regulator5V
Regulator
MC79L05
VS
INPUT RANGE
(V) (V)(1)
20+ 2 to +10
15 2 to +5
12 2 to +2
FIGURE 10. Improved PSR Using External Regulator.
FIGURE 11. Single Supply Operation of the ISO122P Isolation Amplifier. For additional information see AB-009.
NOTE: Since the amplifier is unity gain, the input
range is also the output range. The output can go to
2V since the output section of the ISO amp operates
from dual supplies.
ISO
122P
R1 R2
R4
INA105
Difference Amp
R3
RS
2
3
4
IN4689
5.1V
Reference
5
7
6
1VIN
Signal Source
+
NOTE: (1) Select to match R .S
10k
151
9
V (+15V)S1
+V (+15V)S2
V (15V)S2
162
VS1
Com 2
V = VOUT IN7
8
10
In
Gnd
ISO
122RC
(1)
ISO
122P
ISO
122P
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ISO122
1516
1 2
10 9
ISO122PINPUT
SECTION
OUTPUT
SECTION
7 8
Gnd V IN V V+
V+ V V O Gnd
HPR117
65421
Output
Gnd
VO
VIN
+15V
15V
Auxiliary
Isolated
Power
Output
15V, 20mA
+15V, 20mAInput
Gnd
15V, 20mA
+15V, 20mA
1516
1 2
10 9
ISO122PINPUT
SECTION
OUTPUT
SECTION
7 8
Gnd VIN
V V+
V+ V VO
Gnd
HPR117
456 12
VIN
Input
Gnd
+15V, 20mA
15V, 20mA
Auxiliary
Isolated
Power
Output
HPR117
6541
VO
Output
Gnd
Auxiliary
Isolated
Power
Output
Gnd+15V
2
FIGURE 13. Powered ISO Amp with Three-Port Isolation. For additional information refer to AB-024.
FIGURE 12. Input-Side Powered ISO Amp. For additional information refer to AB-024.
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IMPORTANT NOTICE
Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue
any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TIs standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
Customers are responsible for their applications using TI components.
In order to minimize risks associated with the customers applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TIs publication of information regarding any thirdpartys products or services does not constitute TIs approval, warranty or endorsement thereof.
Copyright 2000, Texas Instruments Incorporated
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