LM3940

1A Low Dropout Regulator for 5V to 3.3V Conversion

General Description

The LM3940 is a 1A low dropout regulator designed to pro-

vide 3.3V from a 5V supply.

The LM3940 is ideally suited for systems which contain both

5V and 3.3V logic, with prime power provided from a 5V bus.

Because the LM3940 is a true low dropout regulator, it can

hold its 3.3V output in regulation with input voltages as low

as 4.5V.

The T0-220 package of the LM3940 means that in most ap-

plications the full 1A of load current can be delivered without

using an additional heatsink.

The surface mount TO-263 package uses minimum board

space, and gives excellent power dissipation capability when

soldered to a copper plane on the PC board.

Features

n Output voltage specified over temperature

n Excellent load regulation

n Guaranteed 1A output current

n Requires only one external component

n Built-in protection against excess temperature

n Short circuit protected

Applications

n Laptop/Desktop Computers

n Logic Systems

Typical Application

DS012080-1

May 1999

© 1999 National Semiconductor Corporation

DS012080

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