LM1578A/LM2578A/LM3578A

Switching Regulator

General Description

The LM1578A is a switching regulator which can easily be

set up for such DC-to-DC voltage conversion circuits as the

buck, boost, and inverting configurations. The LM1578A fea-

tures a unique comparator input stage which not only has

separate pins for both the inverting and non-inverting inputs,

but also provides an internal 1.0V reference to each input,

thereby simplifying circuit design and p.c. board layout. The

output can switch up to 750 mA and has output pins for its

collector and emitter to promote design flexibility. An external

current limit terminal may be referenced to either the ground

or the V

tion, the LM1578A has an on board oscillator, which sets the

Hz to 100 kHz (typical).

The LM1578A is an improved version of the LM1578, offer-

ing higher maximum ratings for the total supply voltage and

output transistor emitter and collector voltages.

Features

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Inverting and non-inverting feedback inputs

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1.0V reference at inputs

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Operates from supply voltages of 2V to 40V

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Output current up to 750 mA, saturation less than 0.9V

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Current limit and thermal shut down

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Duty cycle up to 90%

Applications

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Switching regulators in buck, boost, inverting, and

single-ended transformer configurations

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Motor speed control

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Lamp flasher

Functional Diagram

DS008711-1

April 1998

© 1998 National Semiconductor Corporation

DS008711

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