LM2578A/LM3578A Switching Regulator
February 2005
LM2578A/LM3578A
Switching Regulator
General Description
The LM2578A is a switching regulator which can easily be
set up for such DC-to-DC voltage conversion circuits as the
buck, boost, and inverting configurations. The LM2578A fea-
tures a unique comparator input stage which not only has
separate pins for both the inverting and non-inverting inputs,
but also provides an internal 1.0V reference to each input,
thereby simplifying circuit design and p.c. board layout. The
output can switch up to 750 mA and has output pins for its
collector and emitter to promote design flexibility. An external
current limit terminal may be referenced to either the ground
or the V
in
terminal, depending upon the application. In addi-
tion, the LM2578A has an on board oscillator, which sets the
switching frequency with a single external capacitor from
<
1
Hz to 100 kHz (typical).
The LM2578A is an improved version of the LM2578, offer-
ing higher maximum ratings for the total supply voltage and
output transistor emitter and collector voltages.
Features
n
n
n
n
n
n
Inverting and non-inverting feedback inputs
1.0V reference at inputs
Operates from supply voltages of 2V to 40V
Output current up to 750 mA, saturation less than 0.9V
Current limit and thermal shut down
Duty cycle up to 90%
Applications
n
Switching regulators in buck, boost, inverting, and
single-ended transformer configurations
n
Motor speed control
n
Lamp flasher
Connection Diagram and Ordering Information
Dual-In-Line Package
00871129
Order Number LM3578AM, LM2578AN or LM3578AN
See NS Package Number M08A or N08E
© 2005 National Semiconductor Corporation
DS008711
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
