National LM1577 LM2577 User's Manual

April

LM 1577/LM IM LE ITC tep-U Voltage egulator

LM1577/LM2577 SIMPLE SWITCHER® Step-Up Voltage Regulator General Description Features

The LM1577/LM2577 are monolithic integrated circuits that Requires few external components provide all of the power and control functions for step-up NPN output switches 3.0A, can stand off 65V

(boost), flyback, and forward converter switching regulators. Wide input voltage range: 3.5V to 40V The device is available in three different output voltage

Current-mode operation for improved transient

versions: 12V, 15V, and adjustable.

response, line regulation, and current limit

Requiring minimum number of external components, these k Hz internal oscillator regulators are cost effective, and simple to use. Listed in this

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

data sheet are family of standard inductors and flyback

Output switch protected by current limit, under-voltage

transformers designed to work with these switching regula-

lockout, and thermal shutdown

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

Typical Applications

protection circuitry, consisting of current and thermal limiting,

Simple boost regulator

and undervoltage lockout. Other features include k Hz

Flyback and forward regulators

fixed-frequency oscillator that requires no external compo-

nents, soft start mode to reduce in-rush current during Multiple-output regulator

start-up, and current mode control for improved rejection of input voltage and output load transients.

Connection Diagrams

Straight Leads Bent, Staggered Leads 5-Lead TO-220 (T) 5-Lead TO-220 (T)

View View

Order Number LM2577T-12, LM2577T-15, Order Number LM2577T-12 Flow LB03, LM2577T-15

or LM2577T-ADJ Flow LB03, or LM2577T-ADJ Flow LB03 See NS Package Number T05A See NS Package Number T05D

SIMPLE SWITCHER® is registered trademark of National Semiconductor Corporation.

National Semiconductor Corporation DS011468 www.national.com