LM2594/LM2594HV SIMPLE SWITCHER Power Converter 150 kHz 0.5A Step-Down Voltage
Regulator
December 1999
LM2594/LM2594HV
SIMPLE SWITCHER
®
Power Converter 150 kHz 0.5A
Step-Down Voltage Regulator
General Description
The LM2594/LM2594HV 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 de-
vices are available in fixed output voltages of 3.3V, 5V, 12V,
and an adjustable output version, and are packaged in a
8-lead DIP and a 8-lead surface mount package.
Requiring a minimum number of external components, these
regulators are simple to use and feature internal frequency
compensation
†
, a fixed-frequency oscillator, and improved
line and load regulation specifications.
The LM2594/LM2594HV 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 LM2594/LM2594HV se-
ries. This feature greatly simplifies the design of
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
frequency reducing current limit for the output switch and an
over temperature shutdown for complete protection under
fault conditions.
The LM2594HV is for applications requiring an 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 the HV version)
±
4% max over line and load
conditions
n
Available in 8-pin surface mount and DIP-8 package
n
Guaranteed 0.5A output current
n
Input voltage range up to 60V
n
Requires only 4 external components
n
150 kHz fixed frequency internal oscillator
n
TTL Shutdown capability
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
n
n
n
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to Negative convertor
Typical Application
(Fixed Output Voltage Versions)
DS012439-1
SIMPLE SWITCHER and
Switchers Made Simple
™
are registered trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS012439
www.national.com
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