LM3940 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
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Output voltage specified over temperature
Excellent load regulation
Guaranteed 1A output current
Requires only one external component
Built-in protection against excess temperature
Short circuit protected
Applications
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Laptop/Desktop Computers
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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.
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See Application Hints.
© 1999 National Semiconductor Corporation
DS012080
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