LM2673 SIMPLE SWITCHER 3A Step-Down Voltage Regulator with Adjustable Current Limit
October 2003
LM2673
SIMPLE SWITCHER
®
3A Step-Down Voltage Regulator
with Adjustable Current Limit
General Description
The LM2673 series of regulators are monolithic integrated
circuits which provide all of the active functions for a step-
down (buck) switching regulator capable of driving up to 3A
loads with excellent line and load regulation characteristics.
High efficiency (
>
90%) is obtained through the use of a low
ON-resistance DMOS power switch. The series consists of
fixed output voltages of 3.3V, 5V and 12V and an adjustable
output version.
The SIMPLE SWITCHER concept provides for a complete
design using a minimum number of external components. A
high fixed frequency oscillator (260KHz) allows the use of
physically smaller sized components. A family of standard
inductors for use with the LM2673 are available from several
manufacturers to greatly simplify the design process.
Other features include the ability to reduce the input surge
current at power-ON by adding a softstart timing capacitor to
gradually turn on the regulator. The LM2673 series also has
built in thermal shutdown and resistor programmable current
limit of the power MOSFET switch to protect the device and
load circuitry under fault conditions. The output voltage is
guaranteed to a
±
2% tolerance. The clock frequency is
controlled to within a
±
11% tolerance.
Features
n
Efficiency up to 94%
n
Simple and easy to design with (using off-the-shelf
external components)
n
Resistor programmable peak current limit over a range
of 2A to 5A.
n
150 mΩ DMOS output switch
n
3.3V, 5V and 12V fixed output and adjustable (1.2V to
37V ) versions
n
±
2%maximum output tolerance over full line and load
conditions
n
Wide input voltage range: 8V to 40V
n
260 KHz fixed frequency internal oscillator
n
Softstart capability
n
−40 to +125˚C operating junction temperature range
Applications
n
Simple to design, high efficiency (
>
90%) step-down
switching regulators
n
Efficient system pre-regulator for linear voltage
regulators
n
Battery chargers
Typical Application
10091303
SIMPLE SWITCHER
®
is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS100913
www.national.com
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