LM3940_03 Datasheet, PDF (1/11 Pages) National Semiconductor (TI) – 1A Low Dropout Regulator for 5V to 3.3V Conversion

January 2003
LM3940
1A Low Dropout Regulator for 5V to 3.3V Conversion
General Description
The LM3940 is a 1A low dropout regulator designed to
provide 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
applications 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
*Required if regulator is located more than 1" from the power supply filter capacitor or if battery power is used.
**See Application Hints.
01208001
Connection Diagram/Ordering Information
01208002
3-Lead TO-220 Package
(Front View)
Order Part Number LM3940IT-3.3
NSC Drawing Number TO3B
01208003
3-Lead TO-263 Package
(Front View)
Order Part Number LM3940IS-3.3
NSC Drawing Number TS3B
© 2003 National Semiconductor Corporation DS012080
01208010
3-Lead SOT-223
(Front View)
Order Part Number LM3940IMP-3.3
Package Marked L52B
NSC Drawing Number MP04A
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