LM1577/LM2577 Series
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 ver-
sions: 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
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
Typical Application
Ordering Information
Temperature
Range
Package
Type
Output Voltage
NSC
12V
15V
ADJ
Package Package
Drawing
40C
≤ T
A ≤ +125C
24-Pin Surface Mount
LM2577M-12
LM2577M-15
LM2577M-ADJ
M24B
SO
16-Pin Molded DIP
LM2577N-12
LM2577N-15
LM2577N-ADJ
N16A
N
5-Lead Surface Mount
LM2577S-12
LM2577S-15
LM2577S-ADJ
TS5B
TO-263
5-Straight Leads
LM2577T-12
LM2577T-15
LM2577T-ADJ
T05A
TO-220
5-Bent Staggered
LM2577T-12
LM2577T-15
LM2577T-ADJ
T05D
TO-220
Leads
Flow LB03
55C
≤ T
A ≤ +150C
4-Pin TO-3
LM1577K-12/883 LM1577K-15/883
LM1577K-
ADJ/883
K04A
TO-3
SIMPLE SWITCHER is a registered trademark of National Semiconductor Corporation.
DS011468-1
Note: Pin numbers shown are for TO-220 (T) package.
June 1999
LM1577/LM2577
Series
SIMPLE
SWITCHER
Step-Up
V
oltage
Regulator
1999 National Semiconductor Corporation
DS011468
www.national.com