Device

Operating

Temperature Range

Package

UC3842A, 43A

UC2842A, 43A

HIGH PERFORMANCE

CURRENT MODE

CONTROLLERS

ORDERING INFORMATION

UC3842AD

UC3843AD

TA = 0° to +70°C

TA = – 25° to +85°C

SO–14

SO–14

PIN CONNECTIONS

Order this document by UC3842A/D

D SUFFIX

PLASTIC PACKAGE

CASE 751A

(SO–14)

N SUFFIX

PLASTIC PACKAGE

CASE 626

1

8

1

14

(Top View)

Vref

(Top View)

Compensation

Voltage Feedback

Current Sense

RT/CT

Vref

VCC

Output

Gnd

1

2

3

45

6

7

8

Compensation

NC

Voltage Feedback

NC

Current Sense

NC

RT/CT

NC

VCC

VC

Output

Gnd

Power Ground

1

2

3

4

5

6

7

9

8

10

11

12

13

14

UC3842AN

UC3843AN

Plastic

Plastic

UC2842AD

UC2843AD

SO–14

SO–14

UC2842AN

UC2843AN

Plastic

Plastic

1

MOTOROLA ANALOG IC DEVICE DATA

High Performance

Current Mode Controllers

The UC3842A, UC3843A series of high performance fixed frequency

current mode controllers are specifically designed for off–line and dc–to–dc

converter applications offering the designer a cost effective solution with

minimal external components. These integrated circuits feature a trimmed

oscillator for precise duty cycle control, a temperature compensated

reference, high gain error amplifier, current sensing comparator, and a high

current totem pole output ideally suited for driving a power MOSFET.

Also included are protective features consisting of input and reference

undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting,

programmable output deadtime, and a latch for single pulse metering.

These devices are available in an 8–pin dual–in–line plastic package as

well as the 14–pin plastic surface mount (SO–14). The SO–14 package has

separate power and ground pins for the totem pole output stage.

The UCX842A has UYLO thresholds of 16 V (on) and 10 V (off), ideally

suited for off–line converters. The UCX843A is tailored for lower voltage

applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

Simplified Block Diagram

5.0V

Reference

Latching

PWM

VCC

Undervoltage

Lockout

Oscillator

Error

Amplifier

7(12)

VC

7(11)

Output

6(10)

Power

Ground

5(8)

3(5)

Current

Sense

Input

Vref

8(14)

4(7)

2(3)

1(1)

Gnd

5(9)

RTCT

Voltage

Feedback

Input

R

R

+

–

Vref

Undervoltage

Lockout

Output

Compensation

Pin numbers in parenthesis are for the D suffix SO–14 package.

VCC

© Motorola, Inc. 1996

Rev 1