LM3940 Datasheet, PDF (1/11 Pages) National Semiconductor (TI) – 1A Low Dropout Regulator for 5V to 3.3V Conversion

May 1999
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
*Required if regulator is located more than 1" from the power supply filter capacitor or if battery power is used.
**See Application Hints.
© 1999 National Semiconductor Corporation DS012080
www.national.com