发表时间:2018/7/12 5:09:08 文章来源:广德教育网 手机版


SIMPLE SWITCHER ?5A Flyback Regulator

General Description

The LM2587series of regulators are monolithic integrated circuits specifically designed for flyback,step-up (boost),and forward converter applications.The device is available in 4different output voltage versions:3.3V,5.0V,12V,and adjust-able.

Requiring a minimum number of external components,these regulators are cost effective,and simple to use.Included in the datasheet are typical circuits of boost and flyback regula-tors.Also listed are selector guides for diodes and capacitors and a family of standard inductors and flyback transformers designed to work with these switching regulators.

The power switch is a 5.0A NPN device that can stand-off 65V.Protecting the power switch are current and thermal limiting circuits,and an undervoltage lockout circuit.This IC contains a 100kHz fixed-frequency internal oscillator that permits the use of small magnetics.Other features include soft start mode to reduce in-rush current during start up,cur-rent mode control for improved rejection of input voltage and output load transients and cycle-by-cycle current limiting.An output voltage tolerance of ±4%,within specified input volt-ages and output load conditions,is guaranteed for the power supply system.


n Requires few external components

n Family of standard inductors and transformers n NPN output switches 5.0A,can stand off 65V n Wide input voltage range:4V to 40V

n Current-mode operation for improved transient response,line regulation,and current limit n 100kHz switching frequency

n Internal soft-start function reduces in-rush current during start-up

n Output transistor protected by current limit,under voltage lockout,and thermal shutdown


System Output Voltage Tolerance of ±4%max over line and load conditions

Typical Applications

n Flyback regulator

n Multiple-output regulator n Simple boost regulator n

Forward converter

Flyback Regulator

Ordering Information

Package Type

NSC Package Order Number

Drawing 5-Lead TO-220Bent,Staggered Leads T05D LM2587T-3.3,LM2587T-5.0,LM2587T-12,LM2587T-ADJ 5-Lead TO-263

TS5B LM2587S-3.3,LM2587S-5.0,LM2587S-12,LM2587S-ADJ 5-Lead TO-263Tape and Reel



SIMPLE SWITCHER ?and Switchers Made Simple ?are registered trademarks of National Semiconductor Corporation.


April 1998

LM2587SIMPLE SWITCHER 5A Flyback Regulator

?1999National Semiconductor Corporation DS012316www.national.com

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