LM2597/LM2597HV
SIMPLE SWITCHER
Power Converter 150 kHz 0.5A
Step-Down Voltage Regulator, with Features
General Description
The LM2597/LM2597HV 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, and an adjustable output version, and are packaged in
an 8-lead DIP and an 8-lead surface mount package.
This series of switching regulators is similar to the LM2594
series, with additional supervisory and performance features
added.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation
, improved line and load specifications,
fixed-frequency oscillator, Shutdown /Soft-start, error flag
delay and error flag output.
The LM2597/LM2597HV series operates at a switching fre-
quency of 150 kHz thus allowing smaller sized filter compo-
nents than what would be needed with lower frequency
switching regulators. Because of its high efficiency, the cop-
per traces on the printed circuit board are normally the only
heat sinking needed.
A standard series of inductors (both through hole and sur-
face mount types) are available from several different manu-
facturers optimized for use with the LM2597/LM2597HV se-
ries.
This
feature
greatly
switch-mode power supplies.
Other features include a guaranteed
±
4% tolerance on out-
put voltage under all conditions of input voltage and output
load conditions, and
±
15% on the oscillator frequency. Ex-
ternal shutdown is included, featuring typically 85 μA
standby current. Self protection features include a two stage
current limit for the output switch and an over temperature
shutdown for complete protection under fault conditions.
simplifies
the
design
of
The LM2597HV is for use in applications requiring and input
voltage up to 60V.
Features
n
3.3V, 5V, 12V, and adjustable output versions
n
Adjustable version output voltage range, 1.2V to 37V
(57V for HV version)
±
4% max over line and load
conditions
n
Guaranteed 0.5A output current
n
Available in 8-pin surface mount and DIP-8 package
n
Input voltage range up to 60V
n
150 kHz fixed frequency internal oscillator
n
Shutdown /Soft-start
n
Out of regulation error flag
n
Error output delay
n
Bias Supply Pin (V
) for internal circuitry improves
efficiency at high input voltages
n
Low power standby mode, I
Q
typically 85 μA
n
High Efficiency
n
Uses readily available standard inductors
n
Thermal shutdown and current limit protection
Applications
n
Simple high-efficiency step-down (buck) regulator
n
Efficient pre-regulator for linear regulators
n
On-card switching regulators
n
Positive to Negative converter
Typical Application
(Fixed Output Voltage Versions)
SIMPLE SWITCHER
and Switchers Made Simple
are registered trademarks of National Semiconductor Corporation.
DS012440-1
Patent Number 5,382,918.
December 2000
L
R
2001 National Semiconductor Corporation
DS012440
www.national.com