LM123/LM323A/LM323
3-Amp, 5-Volt Positive Regulator
General Description
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,a1µFsolid 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-
tance.
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.
Features
nGuaranteed 1%initial accuracy (A version)
n3 amp output current
nInternal current and thermal limiting
n0.01Ωtypical output impedance
n7.5V minimum input voltage
n30W power dissipation
nP
+
Product Enhancement tested
Connection Diagram
Typical Applications
Metal Can Package
DS007771-2
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
DS007771-3
*Required if LM123 is more than 4" from filter capacitor.
†Regulator is stable with no load capacitor into resistive loads.
April 1998
LM123/LM323A/LM323 3-Amp, 5-Volt Positive Regulator
© 1999 National Semiconductor Corporation DS007771 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
(Note 5)
Input Voltage 20V
Power Dissipation Internally Limited
Operating Junction Temperature Range
LM123 −55˚C to +150˚C
LM323A −40˚C to +125˚C
LM323 0˚C to +125˚C
Storage Temperature Range −65˚C to +150˚C
Lead Temperature (Soldering, 10 sec.) 300˚C
ESD Tolerance (Note 5) 2000V
LM123 Electrical Characteristics (Note 2)
Parameter Conditions LM123 Units
Min Typ Max
Output Voltage T
j
=25˚C 4.7 5 5.3 V
V
IN
=7.5V, I
OUT
=0A
7.5V ≤V
IN
≤15V 4.6 5.4 V
0A ≤I
OUT
≤3A, P ≤30W
Line Regulation (Note 4) T
j
=25˚C 5 25 mV
7.5V ≤V
IN
≤15V
Load Regulation (Note 4) T
j
=25˚C, V
IN
=7.5V, 25 100 mV
0A ≤I
OUT
≤3A
Quiescent Current 7.5V ≤V
IN
≤15V, 12 20 mA
0A ≤I
OUT
≤3A
Output Noise Voltage T
j
=25˚C 40 µVrms
10 Hz ≤f≤100 kHz
Short Circuit Current Limit T
j
=25˚C
V
IN
=15V 3 4.5 A
V
IN
=7.5V 4 5 A
Long Term Stability 35 mV
Thermal Resistance Junction
to Case (Note 3) 2 ˚C/W
LM323A/LM323 Electrical Characteristics (Note 2)
Parameter Conditions LM323A LM323 Units
Min Typ Max Min Typ Max
Output Voltage T
j
=25˚C 4.95 5 5.05 4.8 5 5.2 V
V
IN
=7.5V, I
OUT
=0A
7.5V ≤V
IN
≤15V 4.85 5.15 4.75 5.25 V
0A ≤I
OUT
≤3A, P ≤30W
Line Regulation (Note 4) T
j
=25˚C 5 10 5 25 mV
7.5V ≤V
IN
≤15V
Load Regulation (Note 4) T
j
=25˚C, V
IN
=7.5V, 25 50 25 100 mV
0A ≤I
OUT
≤3A
Quiescent Current 7.5V ≤V
IN
≤15V, 12 20 12 20 mA
0A ≤I
OUT
≤3A
Output Noise Voltage T
j
=25˚C 40 40 µVrms
10 Hz ≤f≤100 kHz
Short Circuit Current Limit T
j
=25˚C
V
IN
=15V 3 4.5 3 4.5 A
V
IN
=7.5V 4 6 4 5 A
Long Term Stability 35 35 mV
Thermal Resistance Junction
to Case (Note 3) 2 2 ˚C/W
www.national.com 2
LM323A/LM323 Electrical Characteristics (Note 2) (Continued)
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits.
Note 2: Unless otherwise noted, specifications apply for −55˚C ≤Tj≤+150˚C for the LM123, −40˚C ≤Tj≤+125˚C for the LM323A, and 0˚C ≤Tj≤+125˚C for the
LM323. Although power dissipation is internally limited, specifications apply only for P ≤30W.
Note 3: Without a heat sink, the thermal resistance of the TO-3 package is about 35˚C/W. With a heat sink, the effective thermal resistance can only approach the
specified values of 2˚C/W, depending on the efficiency of the heat sink.
Note 4: Load and line regulation are specified at constant junction temperature. Pulse testing is required with a pulse width ≤1 ms and a duty cycle ≤5%.
Note 5: Refer to RETS123K drawing for LM123K military specifications.
Note 6: Human body model, 1.5 kΩin series with 100 pF.
Typical Performance Characteristics
Maximum Average Power
Dissipation for LM123
DS007771-9
Maximum Average Power
Dissipation for LM323A, LM323
DS007771-10
Output Impedance
DS007771-11
Peak Available Output Current
DS007771-12
Short Circuit Current
DS007771-13
Ripple Rejection
DS007771-14
Dropout Voltage
DS007771-15
Line Transient Response
DS007771-16
Output Voltage
DS007771-17
www.national.com3
Typical Performance Characteristics (Continued)
Typical Applications
Quiescent Current
DS007771-18
Load Transient Response
DS007771-19
Output Noise Voltage
DS007771-20
10 Amp Regulator with Complete Overload Protection
DS007771-6
*Select for 20 mA Current from Unregulated Negative Supply
www.national.com 4
Typical Applications (Continued)
Adjustable Regulator 0V−10V @3A
DS007771-7
A1— LM101A
C1— 2 µF Optional— Improves Ripple Rejection, Noise, and Transient Response
Trimming Output to 5V
DS007771-8
Adjustable Output 5V−10V 0.1%Regulation
DS007771-4
*Select to Set Output Voltage
**Select to Draw 25 mA from V−
www.national.com5
Schematic Diagram
DS007771-1
www.national.com 6
Physical Dimensions inches (millimeters) unless otherwise noted
Metal Can Package (K)
Order Number LM123K STEEL, LM323AK STEEL or LM323K STEEL
NS Package Number K02A
www.national.com7
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
National Semiconductor
Europe Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: sea.support@nsc.com
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
Metal Can Package (K)
Mil-Aero Product
Order Number LM123K/883
NS Package Number K02C
LM123/LM323A/LM323 3-Amp, 5-Volt Positive Regulator
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
