June 1999
LM2574/LM2574HV
™
SIMPLE SWITCHER 0.5A Step-Down Voltage Regulator
General Description
Features
n 3.3V, 5V, 12V, 15V, and adjustable output versions
The LM2574 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 0.5A load
with excellent line and load regulation. These devices are
available in fixed output voltages of 3.3V, 5V, 12V, 15V, and
an adjustable output version.
n Adjustable version output voltage range, 1.23V to 37V
(57V for HV version) 4% max over line and load
conditions
n Guaranteed 0.5A output current
n Wide input voltage range, 40V, up to 60V for HV version
n Requires only 4 external components
n 52 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n High efficiency
±
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation and a fixed-frequency oscillator.
The LM2574 series offers a high-efficiency replacement for
popular three-terminal linear regulators. Because of its high
efficiency, the copper traces on the printed circuit board are
normally the only heat sinking needed.
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
A standard series of inductors optimized for use with the
LM2574 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Applications
n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
±
Other features include a guaranteed 4% tolerance on out-
n Positive to negative converter (Buck-Boost)
put voltage within specified input voltages and output load
±
conditions, and 10% on the oscillator frequency. External
shutdown is included, featuring 50 µA (typical) standby cur-
rent. The output switch includes cycle-by-cycle current limit-
ing, as well as thermal shutdown for full protection under
fault conditions.
Typical Application (Fixed Output Voltage Versions)
DS011394-1
Note: Pin numbers are for 8-pin DIP package.
Patent Pending
™
SIMPLE SWITCHER is a trademark of National Semiconductor Corporation
© 1999 National Semiconductor Corporation
DS011394
www.national.com
NSC [ National Semiconductor ]
