CURRENT MODE PWM CONTROLLER

LM3842A/3A/4A/5A

FEATURES

● Automatic feed forward compensation

● Optimized for offline converter

● Double pulse suppression

● Current mode operation to 500 KHz

● High gain totem pole output

● Internally trimmed bandgap reference

● Undervoltage lockout with hysteresis

ORDERING INFORMATION

Device

Package

DESCRIPTION

LM3842A/3A/4A/5A D

8 SOP

LM3842A/3A/4A/5A N

8 DIP

The LM3842A is fixed frequency current-mode PWM controller.

It is specially designed for Off-Line and

DC-to-DC converter applications with minimal external components.

This integrated circuit features a trimmed oscillator for precise duty cycle control, a temperature

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

totempole output ideally suited for driving a power MOSFET.

Protection circuitry includes built in under-voltage lockout and current limiting.

SIMPLIFIED BLOCK DIAGRAM

Characteristic

Symbol

Value

Unit

Power Supply Voltage

30

V

Output Current

I

± 1

A

Analog Inputes Voltage

-0.3 to 5.5V

V

Error Amp Output Sink Current

10

mA

Power Dissipation

1

W

-65 to 150

℃

Lead Temperature (soldering 5 sec)

T

260

℃

HTC

1

5V

Reference

Vcc

Undervoltage

Lockout

Latching

PWM

Oscillator

Undervoltage

Lockout

+

-

Sense

Input

RT/CT

④

VFB

②

COMP

①

Error

Amplifie

r

R

R

1

2

3

4

8

7

6

5

Voltage

Feedback

Current

Sense

Vcc

OUTPUT

GND

Compen

sation

8 SOP/ 8 DIP PIN Configulation