LM2588 SIMPLE SWITCHER 5A Flyback Regulator with Shutdown
April 1998
LM2588
SIMPLE SWITCHER
®
5A Flyback Regulator with
Shutdown
General Description
The LM2588 series of regulators are monolithic integrated
circuits specifically designed for flyback, step-up (boost), and
forward converter applications. The device is available in 4
different output voltage versions: 3.3V, 5.0V, 12V, and adjust-
able.
Requiring a minimum number of external components, these
regulators are cost effective, and simple to use. Included in
the datasheet are typical circuits of boost and flyback regula-
tors. Also listed are selector guides for diodes and capacitors
and a family of standard inductors and flyback transformers
designed to work with these switching regulators.
The power switch is a 5.0A NPN device that can stand-off
65V. Protecting the power switch are current and thermal
limiting circuits, and an undervoltage lockout circuit. This IC
contains an adjustable frequency oscillator that can be pro-
grammed up to 200 kHz. The oscillator can also be synchro-
nized with other devices, so that multiple devices can oper-
ate at the same switching frequency.
Other features include soft start mode to reduce in-rush cur-
rent during start up, and current mode control for improved
rejection of input voltage and output load transients and
cycle-by-cycle current limiting. The device also has a shut-
down pin, so that it can be turned off externally. An output
voltage tolerance of
±
4%, within specified input voltages and
output load conditions, is guaranteed for the power supply
system.
Features
Requires few external components
Family of standard inductors and transformers
NPN output switches 5.0A, can stand off 65V
Wide input voltage range: 4V to 40V
Adjustable switching frequency: 100 kHz to 200 kHz
External shutdown capability
Draws less than 60 µA when shut down
Frequency synchronization
Current-mode operation for improved transient
response, line regulation, and current limit
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Internal soft-start function reduces in-rush current during
start-up
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Output transistor protected by current limit, under
voltage lockout, and thermal shutdown
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System output voltage tolerance of
±
4% max over line
and load conditions
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Typical Applications
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Flyback regulator
Forward converter
Multiple-output regulator
Simple boost regulator
Flyback Regulator
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SIMPLE SWITCHER
®
and
Switchers Made Simple
®
are registered trademarks of National Semiconductor Corporation.
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DS012420
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