UC3842B, 43B

UC2842B, 43B

HIGH PERFORMANCE

CURRENT MODE

CONTROLLERS

Order this document by UC3842B/D

D SUFFIX

PLASTIC PACKAGE

CASE 751A

(SO–14)

N SUFFIX

PLASTIC PACKAGE

CASE 626

D1 SUFFIX

PLASTIC PACKAGE

CASE 751

(SO–8)

8

1

8

1

14

1

Device

Operating

Temperature Range

Package

ORDERING INFORMATION

UC384XBD

UC384XBD1

TA = 0° to +70°C

TA = – 25° to +85°C

SO–14

UC384XBN

UC284XBD

UC284XBD1

UC284XBN

UC384XBVD

UC384XBVD1

UC384XBVN

TA = – 40° to +105°C

SO–8

Plastic

SO–14

SO–8

Plastic

SO–14

SO–8

Plastic

PIN CONNECTIONS

Compensation

NC

Voltage Feedback

NC

Current Sense

NC

RT/CT

Compensation

Voltage Feedback

Current Sense

RT/CT

Vref

Vref

NC

VCC

VC

Output

Gnd

Power Ground

VCC

Output

Gnd

(Top View)

8

7

6

5

1

2

3

4

1

2

3

4

14

13

12

11

5

6

7

10

9

8

(Top View)

X indicates either a 2 or 3 to define specific device part

numbers.

1

MOTOROLA ANALOG IC DEVICE DATA

High Performance

Current Mode Controllers

The UC3842B, UC3843B series are high performance fixed frequency

current mode controllers. They 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 and surface mount

(SO–8) 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 UCX842B has UVLO thresholds of 16 V (on) and 10 V (off), ideally

suited for off–line converters. The UCX843B 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)

RT/CT

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