3-Amp, 5-Volt Positive Regulator
The LM123 is a three-terminal positive regulator with a pre-
set 5V output and a load driving capability of 3 amps. New
circuit design and processing techniques are used to provide
the high output current without sacrificing the regulation
characteristics of lower current devices.
The LM323A offers improved precision over the standard
LM323. Parameters with tightened specifications include
output voltage tolerance, line regulation, and load regulation.
The 3 amp regulator is virtually blowout proof. Current limit-
ing, power limiting, and thermal shutdown provide the same
high level of reliability obtained with these techniques in the
LM109 1 amp regulator.
No external components are required for operation of the
LM123. If the device is more than 4 inches from the filter ca-
pacitor, however, a 1 µF solid tantalum capacitor should be
used on the input. A 0.1 µF or larger capacitor may be used
on the output to reduce load transient spikes created by fast
switching digital logic, or to swamp out stray load capaci-
An overall worst case specification for the combined effects
of input voltage, load currents, ambient temperature, and
power dissipation ensure that the LM123 will perform satis-
factorily as a system element.
For applications requiring other voltages, see LM150 series
adjustable regulator data sheet.
Operation is guaranteed over the junction temperature range
−55˚C to +150˚C for LM123, −40˚C to +125˚C for LM323A,
and 0˚C to +125˚C for LM323. A hermetic TO-3 package is
used for high reliability and low thermal resistance.
n Guaranteed 1% initial accuracy (A version)
n 3 amp output current
n Internal current and thermal limiting
n 0.01Ω typical output impedance
n 7.5V minimum input voltage
n 30W power dissipation
n P+ Product Enhancement tested
Metal Can Package
Order Number LM123K STEEL, LM323AK STEEL or LM323K STEEL
See NS Package Number K02A
Order Number LM123K/883
See NS Package Number K02C
Basic 3 Amp Regulator
*Required if LM123 is more than 4" from filter capacitor.
†Regulator is stable with no load capacitor into resistive loads.
© 1999 National Semiconductor Corporation DS007771