LM1577/LM2577 Series SIMPLE SWITCHER® Step-Up Voltage Regulator

Features

♦ Requires few external components

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

♦ Wide input voltage range: 3.5V to 40V

♦ Current-mode operation for improved transient response, line regulation, and current limit

♦ 52 kHz internal oscillator

♦ Soft-start function reduces in-rush current during start-up ♦ Output switch protected by current limit, under-voltage lockout, and thermal shutdown

Typical Applications

♦ Simple boost regulator

♦ Flyback and forward regulators

♦ Multiple-output regulator

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.

Typical Application