LM2672 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator
with Features
April 2007
LM2672
SIMPLE SWITCHER
®
Power Converter High Efficiency 1A
Step-Down Voltage Regulator with Features
General Description
The LM2672 series of regulators are monolithic integrated
circuits built with a LMDMOS process. These regulators pro-
vide all the active functions for a step-down (buck) switching
regulator, capable of driving a 1A load current with excellent
line and load regulation. These devices are available in fixed
output voltages of 3.3V, 5.0V, 12V, and an adjustable output
version.
Requiring a minimum number of external components, these
regulators are simple to use and include patented internal
frequency compensation (Patent Nos. 5,382,918 and
5,514,947), fixed frequency oscillator, external shutdown,
soft-start, and frequency synchronization.
The LM2672 series operates at a switching frequency of
260 kHz, thus allowing smaller sized filter components than
what would be needed with lower frequency switching regu-
lators. Because of its very high efficiency (>90%), the copper
traces on the printed circuit board are the only heat sinking
needed.
A family of standard inductors for use with the LM2672 are
available from several different manufacturers. This feature
greatly simplifies the design of switch-mode power supplies
using these advanced ICs. Also included in the datasheet are
selector guides for diodes and capacitors designed to work in
switch-mode power supplies.
Other features include a guaranteed ±1.5% tolerance on out-
put voltage within specified input voltages and output load
conditions, and ±10% on the oscillator frequency. External
shutdown is included, featuring typically 50
μA
stand-by cur-
rent. The output switch includes current limiting, as well as
thermal shutdown for full protection under fault conditions.
To simplify the LM2672 buck regulator design procedure,
there exists computer design software,
LM267X Made Sim-
ple
version 6.0.
Features
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Efficiency up to 96%
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Available in SO-8, 8-pin DIP and LLP packages
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Computer Design Software
LM267X Made Simple
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version 6.0
Simple and easy to design with
Requires only 5 external components
Uses readily available standard inductors
3.3V, 5.0V, 12V, and adjustable output versions
Adjustable version output voltage range: 1.21V to 37V
±1.5% max output voltage tolerance over line and load
conditions
Guaranteed 1A output load current
0.25Ω
DMOS Output Switch
Wide input voltage range: 8V to 40V
260 kHz fixed frequency internal oscillator
TTL shutdown capability, low power standby mode
Soft-start and frequency synchronization
Thermal shutdown and current limit protection
Typical Applications
■
Simple High Efficiency (>90%) Step-Down (Buck)
Regulator
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Efficient Pre-Regulator for Linear Regulators
Typical Application
(Fixed Output Voltage Versions)
1293401
SIMPLE SWITCHER
®
is a registered trademark of National Semiconductor Corporation
Windows
®
is a registered trademark of Microsoft Corporation.
© 2007 National Semiconductor Corporation
12934
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