current-mode pwm controller

1FEATURESD PACKAGE

(TOP VIEW)

1

2

3

4

8

7

6

5

COMP

VFB

ISENSE

RT/CT

VREF

VCC

OUTPUT

GND

DESCRIPTION/ORDERING INFORMATION

UC2843A-Q1

www.ti.com........................................................................................................................................................................................................ SGLS384–MAY 2008

CURRENT-MODE PWM CONTROLLER

• Qualified for Automotive Applications• Extended Temperature Performance of

–40°C to 125°C• Optimized for Off-Line and DC-to-DC

Converters• Low Start-Up Current (<0.5 mA)• Trimmed Oscillator-Discharge Current• Automatic Feed-Forward Compensation• Pulse-by-Pulse Current Limiting• Enhanced Load-Response Characteristics• Under-Voltage Lockout With Hysteresis• Double-Pulse Suppression• High-Current Totem-Pole Output• Internally Trimmed Bandgap Reference• 500-kHz Operation• Low RO Error Amp

The UC2843A control IC is a pin-for-pin compatible improved version of the UC2843. Providing the necessaryfeatures to control current mode switched mode power supplies, this device has the following improved features.Start up current is specified to be less than 0.5 mA. Oscillator discharge is trimmed to 8.3 mA. Duringundervoltage lockout, the output stage can sink at least 10 mA at less than 1.2 V for VCC over 5 V.

MAXIMUM DUTYPART NUMBER UVLO ON UVLO OFF CYCLEUC2843A 8.5 V 7.9 V <100%

ORDERING INFORMATION (1)

TA PACKAGE (2) ORDERABLE PART NUMBER TOP-SIDE MARKING–40°C to 125°C SOIC-8 – D8 Reel of 2500 UC2843AQD8RQ1 UC2843AQ

(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TIweb site at www.ti.com.

(2) Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available atwww.ti.com/sc/package.

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Copyright © 2008, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty. Production processing does notnecessarily include testing of all parameters.

http://focus.ti.com/docs/prod/folders/print/uc2843a-q1.html

CurrentSenseComparator

PWMLatch

GND

Output

VC

V

5 V50 mA

REF

VCC

GND

R /CT T

VFB

COMP

ISENSE

InternalBias

S/R5-VREF

V

GoodLogic

REF

UVLO34 V

2.5 V

Osc

ErrorAmp S

R

2R

R1 V

7

5

4

2

1

3

5

6

7

8

ABSOLUTE MAXIMUM RATINGS (1) (2)

UC2843A-Q1

SGLS384–MAY 2008........................................................................................................................................................................................................ www.ti.com

FUNCTIONAL BLOCK DIAGRAM

over operating free-air temperature range (unless otherwise noted)

VALUE UNITVCC voltage (low impedance source) 30 VVCC voltage (ICC mA) Self limiting

IO Output current ±1 AOutput energy (capacitive load) 5 µJAnalog inputs (pins 3 and 5) –0.3 to 6.3 VError amplifier output sink current 10 mAPower dissipation at TA < 25°C (14-pin D package) 1 W

θJA Package thermal impedance (3) 97 °C/WTstg Storage temperature range –65 to 150 °C

Lead temperature soldering 1,6 mm (1/16 inch) from case for 10 seconds 260 °C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratingsonly, and functional operation of the device at these or any other conditions beyond those indicated under Recommended OperatingConditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) Unless otherwise indicated, voltages are reference to ground, and currents are positive into and negative out of the specified terminals.(3) Long-term high-temperature storage and/or extended use at maximum recommended operating conditions may result in a reduction of

overall device life. See http://www.ti.com/ep_quality for additional information on enhanced plastic packaging.

2 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated

Product Folder Link(s): UC2843A-Q1


http://www.ti.com/ep_quality

http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SGLS384&partnum=UC2843A-Q1


ELECTRICAL CHARACTERISTICS

UC2843A-Q1


TA = –40°C to 125°C, VCC = 15 V (1), RT = 10 kΩ, CT = 3.3 nF, TA = TJ (unless otherwise stated)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITReference SectionOutput voltage TJ = 25°C, IO = 1 mA 4.95 5.0 5.05 VLine regulation voltage VIN = 12 V to 25 V 6 20 mVLoad regulation voltage IO = 1 mA to 20 mA 6 25 mVTemperature stability (2) (3) 0.2 0.4 mV/°CTotal output variation voltage Line, load, temperature 4.9 5.1 VOutput noise voltage f = 10 Hz to 10 kHz TJ = 25°C 50 µVLong term stability 1000 hours TA = 125°C 5 25 mVOutput short-circuit current –30 –100 –180 mAOscillator SectionInitial accuracy (4) TJ = 25°C 47 52 57 kHzVoltage stability VCC = 12 V to 25 V 0.2 1 %Temperature stability TA = MIN to MAX 5 %Amplitude peak-to-peak V pin 7 1.7 V

TJ = 25°C 7.8 8.3 8.8Discharge current (5) V pin 7 = 2 V mA

TJ = Full range 7.5 8.8Error Amplifier SectionInput voltage COMP = 2.5 V 2.45 2.5 2.55 VInput bias current –0.3 –1 µAOpen loop voltage gain (AVOL) VO = 2 V to 4 V 65 90 dBUnity gain bandwidth (3) TJ = 25°C 0.7 1 MHzPSRR VCC = 12 V to 25 V 60 70 dBOutput sink current FB = 2.7 V, COMP = 1.1 V 2 6 mAOutput source current FB = 2.3 V, COMP = 5 V –0.5 –0.8 mAVOUT high FB = 2.3 V, RL = 15 kΩ to GND 5 6 VVOUT low FB = 2.7 V, RL = 15 kΩ to VREF 0.7 1.1 VCurrent Sense SectionGain (6) (7) 2.85 3 3.15 V/VMaximum input signal (6) COMP = 5 V 0.9 1 1.1 VPSRR (6) VCC = 12 V to 25 V 70 dBInput bias current –2 –10 µADelay to output (3) ISENSE = 0 V to 2 V 150 300 ns

(1) Adjust VCC above the start threshold before setting at 15 V.(2) Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:

Temperature Stability = (VREF (max) – VREF (min))/(TJ (max) – TJ (min)). VREF (max) and VREF (min) are the maximum and minimumreference voltage measured over the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at theextremes in temperature.

(3) Specified by design.(4) Output frequency equals oscillator frequency for the UC2843A.(5) This parameter is measured with RT = 10 kΩ to VREF. This contributes approximately 300 µA of current to the measurement. The total

current flowing into the RT/RC pin is approximately 300 µA higher than the measured value.(6) Parameter measured at trip point of latch with VFB at 0 V.(7) Gain is defined by: A = ΔVCOMP/ΔVSENSE; 0 ≤ VSENSE ≤ 0.8 V.

Copyright © 2008, Texas Instruments Incorporated Submit Documentation Feedback 3





UC2843A-Q1


ELECTRICAL CHARACTERISTICS (continued)TA = –40°C to 125°C, VCC = 15 V, RT = 10 kΩ, CT = 3.3 nF, TA = TJ (unless otherwise stated)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITOutput Section (OUT)

IOUT = 20 mA 0.1 0.4Low level output voltage V

IOUT = 200 mA 15 2.2IOUT = –20 mA 13 13.5

High level output voltage VIOUT = –200 mA 12 13.5

Rise time (8) CL = 1 nF TJ = 25°C 50 150 nsFall time (8) CL = 1 nF TJ = 25°C 50 150 nsUVLO saturation VCC = 5 V, IOUT = 10 mA 0.7 1.2 VUndervoltage Lockout Section (UVLO)Start threshold 7.8 8.4 9 VMinimum operation voltage after 7 7.6 8.2 Vturn onPWM SectionMaximum duty cycle 94 96 100 %Minimum duty cycle 0 %Total Standby CurrentStart-up current 0.3 0.5 mAOperating supply current FB = 0 V, SENSE = 0 V 11 17 mAVCC internal zener voltage ICC = 25 mA 30 34 V

(8) Specified by design.






PARAMETER MEASUREMENT INFORMATION

2.5 V

0.5 mA

Comp

VFB

Zi

Zf

2

1

On/Off Commandto Rest of IC

VCC

VON

VOFF

ICC

<17 mA

< 0.5 mA

VOFF VON

VCC

During UVLO, the output is low.

8.4 V

7.6 V

UC2843A

Error

Amp

Current

Sense

Comparator

COMP

Current

Sense

GND

IS

R

CRS

2R

R1 V

1

3

5

UC2843A-Q1


A. The error amplifier can source up to 0.5 mA and sink up to 2 mA.

Figure 1. Error Amp Configuration

Figure 2. Undervoltage Lockout

A. Peak current (Is) is determined by the formula: Ismax = 1.0 V/RSA small RC filter may be required to supress switch transients.

Figure 3. Current Sense Circuit






Error Amplifier Open-Loop Frequency Response

Vo

ltag

e G

ain

– d

B

Frequency – Hz

Ph

as

e –

°

0

-45

-90

-135

-180

80

60

40

20

0

10 100 1k 10k 100k 1M 10M

AV

f

V = 15 VCC

T = 25°CA

T = –55°CA

Source Sat (V – V )CC OH

Sink Sat (V )OL

Output Saturation Characteristics

Sa

tura

tio

nV

olt

ag

e –

V

Output Current, Source or Sink – A

.01 .02 .03 .04 .05 .07 .1 .2 .3 .4 .5 .7 10

1

2

3

4

UC2843A-Q1


PARAMETER MEASUREMENT INFORMATION (continued)

Figure 4. Figure 5.






APPLICATION INFORMATION

Oscillator Frequency vs Timing Resistance Maximum Duty Cycle vs Timing Resistor

VREF

VCC

OUTPUT

GND

CT

1 kW 1 W

0.1 µF

0.1 µF

RT

2N2222

5 k

I

Adjust

W

SENSE

4.7 kW

4.7 kW

1 k

Error Amp

Adjust

W

COMP

UC2843A

VFB

ISENSE

R /CT T GND

OUTPUT

VCC

VREF

100 kW

1

2

3

4 5

6

7

8

UC2843A-Q1


Figure 6. Oscillator

A. High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypasscapacitors should be connected close to pin 5 in a single point ground. The transistor and 5k potentiometer are usedto sample the oscillator waveform and apply an adjustable ramp to pin 3.

Figure 7. Open-Loop Laboratory Text Fixture






A fraction of the oscillator ramp can be resistively summedwith the current sense signal to provide slope compensationfor converters requiring duty cycles over 50%.Note that capacitor C forms a filter with R2 to suppress theleading-edge switch spikes.

RSENSE

ISENSE

R2R1

C

RT

CT

0.1 µF

VREF

R /CT T

ISENSE

UC2843A

8

4

3

Power Supply Specifications

1. Input Voltage 95 VAC to 130 VAC (50 Hz/60 Hz)

2. Line Isolation 3750 V

3. Switching Frequency 40 kHz

4. Efficiency, Full Load 70%

5. Output Voltage:

A. 5%; 1-A to 4-A Load5 V ±

B. 3%; 0.1-A to 0.3-A Load; Ripple voltage: 100 mV P-P Max±12 V

C. -12 V 3%; 0.1-A to 0.3-A Load; Ripple voltage: 100 mV P-P Max±

R151 W

W

117 VACVAROVM 68

C1250 µF250 V

R256 k2 W

W

R124.7 k2 W

W

R44.7 kW

R320 kW

C93300 pF600 V

D41N3613

NP

C122200 µF16 V

C132200 µF16 V

C114700 µF10 V

N5

N12

C104700 µF10 V

N12

D8UES1002

C8680 pF600V

D51N3613

+5 V

COM

+12 V

±12 V COM

–12 V

R112.7 k2 W

W

Q1UFN833

R100.551 W

WR1320 kW

R81 kW

C7470 pF

USD1120

R722 W

T1(Note 2)

D6USD945

L1(Note 2)

R9683 W

W

C447 µF25 V

C322 µF

C2100 µF25 V

R5150 kW

C14100 pF

R610 kW

C6.0022 µF

C5.01 µF

D21N3612

D31N3612

NC

UC2843A

1

2

34 5

6

7

8

D7USF1002

UC2843A-Q1


Figure 8. Slope Compression

Figure 9. Off-Line Flyback Regulator






PACKAGE OPTION ADDENDUM

www.ti.com 6-Apr-2015

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status(1)

Package Type PackageDrawing

Pins PackageQty

Eco Plan(2)

Lead/Ball Finish(6)

MSL Peak Temp(3)

Op Temp (°C) Device Marking(4/5)

Samples

UC2843AQD8RG4Q1 ACTIVE SOIC D 8 2500 Green (RoHS& no Sb/Br)

CU NIPDAU Level-1-260C-UNLIM -40 to 125 (2843AQ ~ UC2843AQ)

UC2843AQD8RQ1 ACTIVE SOIC D 8 2500 Green (RoHS& no Sb/Br)

CU NIPDAU Level-1-260C-UNLIM -40 to 125 (2843AQ ~ UC2843AQ)

(1) The marketing status values are defined as follows:ACTIVE: Product device recommended for new designs.LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.PREVIEW: Device has been announced but is not in production. Samples may or may not be available.OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availabilityinformation and additional product content details.TBD: The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement thatlead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used betweenthe die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weightin homogeneous material)

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuationof the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finishvalue exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken andcontinues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

http://www.ti.com/product/UC2843A-Q1?CMP=conv-poasamples#samplebuy

http://www.ti.com/product/UC2843A-Q1?CMP=conv-poasamples#samplebuy

http://www.ti.com/productcontent

PACKAGE OPTION ADDENDUM

www.ti.com 6-Apr-2015

Addendum-Page 2

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

OTHER QUALIFIED VERSIONS OF UC2843A-Q1 :

• Catalog: UC2843A

NOTE: Qualified Version Definitions:

• Catalog - TI's standard catalog product

http://focus.ti.com/docs/prod/folders/print/uc2843a.html

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device PackageType

PackageDrawing

Pins SPQ ReelDiameter

(mm)

ReelWidth

W1 (mm)

A0(mm)

B0(mm)

K0(mm)

P1(mm)

W(mm)

Pin1Quadrant

UC2843AQD8RQ1 SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 24-Oct-2015

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

UC2843AQD8RQ1 SOIC D 8 2500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 24-Oct-2015

Pack Materials-Page 2

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and otherchanges to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latestissue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current andcomplete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of salesupplied at the time of order acknowledgment.TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s termsand conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessaryto support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarilyperformed.TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products andapplications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provideadequate design and operating safeguards.TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, orother intellectual property right relating to any combination, machine, or process in which TI components or services are used. Informationpublished by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty orendorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of thethird party, or a license from TI under the patents or other intellectual property of TI.Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alterationand is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altereddocumentation. Information of third parties may be subject to additional restrictions.Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or servicevoids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.TI is not responsible or liable for any such statements.Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirementsconcerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or supportthat may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards whichanticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might causeharm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the useof any TI components in safety-critical applications.In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is tohelp enable customers to design and create their own end-product solutions that meet applicable functional safety standards andrequirements. Nonetheless, such components are subject to these terms.No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the partieshave executed a special agreement specifically governing such use.Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use inmilitary/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI componentswhich have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal andregulatory requirements in connection with such use.TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use ofnon-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

Products ApplicationsAudio www.ti.com/audio Automotive and Transportation www.ti.com/automotiveAmplifiers amplifier.ti.com Communications and Telecom www.ti.com/communicationsData Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computersDLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-appsDSP dsp.ti.com Energy and Lighting www.ti.com/energyClocks and Timers www.ti.com/clocks Industrial www.ti.com/industrialInterface interface.ti.com Medical www.ti.com/medicalLogic logic.ti.com Security www.ti.com/securityPower Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defenseMicrocontrollers microcontroller.ti.com Video and Imaging www.ti.com/videoRFID www.ti-rfid.comOMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.comWireless Connectivity www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265Copyright © 2015, Texas Instruments Incorporated

http://www.ti.com/audio

http://www.ti.com/automotive

http://amplifier.ti.com

http://www.ti.com/communications

http://dataconverter.ti.com

http://www.ti.com/computers

http://www.dlp.com

http://www.ti.com/consumer-apps

http://dsp.ti.com

http://www.ti.com/energy

http://www.ti.com/clocks

http://www.ti.com/industrial

http://interface.ti.com

http://www.ti.com/medical

http://logic.ti.com

http://www.ti.com/security

http://power.ti.com

http://www.ti.com/space-avionics-defense

http://microcontroller.ti.com

http://www.ti.com/video

http://www.ti-rfid.com

http://www.ti.com/omap

http://e2e.ti.com

http://www.ti.com/wirelessconnectivity

current-mode pwm controller

Documents