LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator
April 2005
LM1577/LM2577
SIMPLE SWITCHER
®
Step-Up Voltage 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 regula-
tors.
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 compo-
nents, 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
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
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52 kHz internal oscillator
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Soft-start function reduces in-rush current during start-up
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Output switch protected by current limit, under-voltage
lockout, and thermal shutdown
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Typical Applications
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Simple boost regulator
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Flyback and forward regulators
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Multiple-output regulator
Connection Diagrams
Straight Leads
5-Lead TO-220 (T)
Bent, Staggered Leads
5-Lead TO-220 (T)
01146804
01146805
Top View
Order Number LM2577T-12, LM2577T-15,
or LM2577T-ADJ
See NS Package Number T05A
Top View
Order Number LM2577T-12 Flow LB03, LM2577T-15
Flow LB03, or LM2577T-ADJ Flow LB03
See NS Package Number T05D
SIMPLE SWITCHER
®
is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS011468
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
