UC2843AQD8RQ1 - Texas Instruments

FEATURES

D PACKAGE

(TOP VIEW)

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-DCConverters

•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 R

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 V

over 5 V.MAXIMUM DUTYPART NUMBER UVLO ON UVLO OFF

CYCLE

UC2843A 8.5 V 7.9 V <100%

ORDERING INFORMATION

(1)

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.

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.

Current

Sense

Comparator

PWM

Latch

GND

Output

5 V

50 mA

REF

VCC

GND

R /C

T T

VFB

COMP

ISENSE

Internal

Bias

S/R 5-V

REF

Good

Logic

REF

UVLO

34 V

2.5 V

Osc

Error

Amp S

R1 V

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 UNIT

voltage (low impedance source) 30 VV

voltage (I

mA) Self limitingI

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 T

< 25 °C (14-pin D package) 1 Wθ

Package thermal impedance

(3)

97 °C/WT

stg

Storage temperature range – 65 to 150 °CLead 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 ofoverall device life. See http://www.ti.com/ep_quality for additional information on enhanced plastic packaging.

Product Folder Link(s): UC2843A-Q1

ELECTRICAL CHARACTERISTICS

UC2843A-Q1

www.ti.com

= – 40 °C to 125 °C, V

= 15 V

(1)

, R

= 10 k Ω, C

= 3.3 nF, T

= T

(unless otherwise stated)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Reference Section

Output voltage T

= 25 °C, I

= 1 mA 4.95 5.0 5.05 VLine regulation voltage V

= 12 V to 25 V 6 20 mVLoad regulation voltage I

= 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 T

= 25 °C 50 µVLong term stability 1000 hours T

= 125 °C 5 25 mVOutput short-circuit current – 30 – 100 – 180 mA

Oscillator Section

Initial accuracy

(4)

= 25 °C 47 52 57 kHzVoltage stability V

= 12 V to 25 V 0.2 1 %Temperature stability T

= MIN to MAX 5 %Amplitude peak-to-peak V pin 7 1.7 VT

= 25 °C 7.8 8.3 8.8Discharge current

(5)

V pin 7 = 2 V mAT

= Full range 7.5 8.8

Error Amplifier Section

Input voltage COMP = 2.5 V 2.45 2.5 2.55 VInput bias current – 0.3 – 1 µAOpen loop voltage gain (AVOL) V

= 2 V to 4 V 65 90 dBUnity gain bandwidth

(3)

= 25 °C 0.7 1 MHzPSRR V

= 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 k Ωto GND 5 6 VVOUT low FB = 2.7 V, RL = 15 k Ωto V

REF

0.7 1.1 V

Current Sense Section

Gain

(6) (7)

2.85 3 3.15 V/VMaximum input signal

(6)

COMP = 5 V 0.9 1 1.1 VPSRR

(6)

= 12 V to 25 V 70 dBInput bias current – 2 – 10 µADelay to output

(3)

SENSE

= 0 V to 2 V 150 300 ns

(1) Adjust V

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 = (V

REF

(max) – V

REF

(min))/(T

(max) – T

(min)). V

REF

(max) and V

REF

(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 R

= 10 k Ωto V

REF

. This contributes approximately 300 µA of current to the measurement. The totalcurrent flowing into the R

pin is approximately 300 µA higher than the measured value.(6) Parameter measured at trip point of latch with V

at 0 V.(7) Gain is defined by: A = ΔV

COMP

/ΔV

SENSE

; 0 ≤V

SENSE

≤0.8 V.

Product Folder Link(s): UC2843A-Q1

UC2843A-Q1

www.ti.com

ELECTRICAL CHARACTERISTICS (continued)T

= – 40 °C to 125 °C, V

= 15 V , R

= 10 k Ω, C

= 3.3 nF, T

= T

(unless otherwise stated)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Output Section (OUT)

OUT

= 20 mA 0.1 0.4Low level output voltage VI

OUT

= 200 mA 15 2.2I

OUT

= – 20 mA 13 13.5High level output voltage VI

OUT

= – 200 mA 12 13.5Rise time

(8)

= 1 nF T

= 25 °C 50 150 nsFall time

(8)

= 1 nF T

= 25 °C 50 150 nsUVLO saturation V

= 5 V, I

OUT

= 10 mA 0.7 1.2 V

Undervoltage Lockout Section (UVLO)

Start threshold 7.8 8.4 9 VMinimum operation voltage after

7 7.6 8.2 Vturn on

PWM Section

Maximum duty cycle 94 96 100 %Minimum duty cycle 0 %

Total Standby Current

Start-up current 0.3 0.5 mAOperating supply current FB = 0 V, SENSE = 0 V 11 17 mAV

internal zener voltage I

= 25 mA 30 34 V

(8) Specified by design.

Product Folder Link(s): UC2843A-Q1

PARAMETER MEASUREMENT INFORMATION

2.5 V

0.5 mA

Comp

VFB

On/Off Command

to 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

R1 V

UC2843A-Q1

www.ti.com

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/R

SA small RC filter may be required to supress switch transients.

Figure 3. Current Sense Circuit

Product Folder Link(s): UC2843A-Q1

Error Amplifier Open-Loop Frequency Response

Voltage Gain – dB

Frequency – Hz

Phase – °

-45

-90

-135

-180

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

V = 15 V

T = 25°C

T = –55°C

Source Sat (V – V )

CC OH

Sink Sat (V )

Output Saturation Characteristics

Saturation Voltage – V

Output Current, Source or Sink – A

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

UC2843A-Q1

www.ti.com

PARAMETER MEASUREMENT INFORMATION (continued)

Figure 4. Figure 5.

Product Folder Link(s): UC2843A-Q1

APPLICATION INFORMATION

Oscillator Frequency vsTiming Resistance Maximum Duty Cycle vsTiming Resistor

VREF

VCC

OUTPUT

GND

1 kW1 W

0.1 µF

2N2222

5 k

Adjust

SENSE

4.7 kW

1 k

Error Amp

Adjust

COMP

UC2843A

VFB

ISENSE

R /C

T T GND

OUTPUT

VCC

VREF

100 kW

UC2843A-Q1

www.ti.com

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

Product Folder Link(s): UC2843A-Q1

A fraction of the oscillator ramp can be resistively summed

with the current sense signal to provide slope compensation

for converters requiring duty cycles over 50%.

Note that capacitor C forms a filter with R2 to suppress the

leading-edge switch spikes.

RSENSE

ISENSE

0.1 µF

VREF

R /C

T T

ISENSE

UC2843A

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±

1 W

117 VAC VARO

VM 68 C1

250 µF

250 V

56 k

2 W

R12

4.7 k

2 W

4.7 kW

20 kW

3300 pF

600 V

1N3613

C12

2200 µF

16 V

C13

2200 µF

16 V

C11

4700 µF

10 V

N12

C10

4700 µF

10 V

N12

UES1002

680 pF

600V

1N3613

+5 V

COM

+12 V

±12 V COM

–12 V

R11

2.7 k

2 W

UFN833

R10

0.55

1 W

R13

20 kW

1 kW

470 pF

USD1120

22 W

(Note 2) D6

USD945

(Note 2)

3 W

47 µF

25 V

22 µF

100 µF

25 V

150 kW

C14

100 pF

10 kW

.0022 µF

.01 µF

1N3612

UC2843A

USF1002

UC2843A-Q1

www.ti.com

Figure 8. Slope Compression

Figure 9. Off-Line Flyback Regulator

Product Folder Link(s): UC2843A-Q1

PACKAGING INFORMATION

Orderable Device Status (1) Package

Type Package

Drawing Pins Package

Qty Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)

UC2843AQD8RG4Q1 ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br) CU NIPDAU Level-1-260C-UNLIM

UC2843AQD8RQ1 ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br) CU NIPDAU Level-1-260C-UNLIM

(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 availability information 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 that lead 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 between the 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 weight in homogeneous material)

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

temperature.

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provided. TI bases its knowledge and belief on information provided 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 and continues to take

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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.

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

PACKAGE OPTION ADDENDUM

www.ti.com 19-Jan-2009

Addendum-Page 1

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