LM2671_07 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – SIMPLE SWITCHER® Power Converter High Efficiency 500mA Step-Down Voltage Regulator with Features

April 2007
LM2671
SIMPLE SWITCHER^® Power Converter High Efficiency
500mA Step-Down Voltage Regulator with Features
General Description
The LM2671 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 500mA load current with ex-
cellent 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 LM2671 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 LM2671 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 LM2671 buck regulator design procedure,
there exists computer design software, LM267X Made Sim-
ple (version 6.0).
Features
■ ^{Efficiency up to 96%}
■ ^{Available in SO-8, 8-pin DIP and LLP packages}
■ ^{Computer Design Software LM267X Made Simple}
(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 500mA 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}
Applications
■ ^{Simple High Efficiency (>90%) Step-Down (Buck)}
Regulator
■ ^{Efficient Pre-Regulator for Linear Regulators}
Typical Application
(Fixed Output Voltage Versions)
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