General Description

The LM1577/LM2577 are monolithic integrated circuits that

provide all of the power and control functions for step-up

(boost), flyback, and forward converter switching regulators.

The device is available in three different output voltage versions:

12V, 15V, and adjustable.

Requiring a minimum number of external components, these

regulators are cost effective, and simple to use. Listed in this

data sheet are a family of standard inductors and flyback

transformers designed to work with these switching regulators.

Included on the chip is a 3.0A NPN switch and its associated

protection circuitry, consisting of current and thermal limiting,

and undervoltage lockout. Other features include a 52 kHz

fixed-frequency oscillator that requires no external components,

a soft start mode to reduce in-rush current during

start-up, and current mode control for improved rejection of

input voltage and output load transients.

Features

n Requires few external components

n NPN output switches 3.0A, can stand off 65V

n Wide input voltage range: 3.5V to 40V

n Current-mode operation for improved transient

response, line regulation, and current limit

n 52 kHz internal oscillator

n Soft-start function reduces in-rush current during start-up

n Output switch protected by current limit, under-voltage

lockout, and thermal shutdown

Typical Applications

n Simple boost regulator

n Flyback and forward regulators

n Multiple-output regulator