Product details


Output options Fixed Output Iout (Max) (A) 3 Vin (Max) (V) 20 Vin (Min) (V) 7.5 Vout (Max) (V) 5 Vout (Min) (V) 5 Fixed output options (V) 5 Noise (uVrms) 40 Iq (Typ) (mA) 12 Thermal resistance θJA (°C/W) 35 Load capacitance (Min) (µF) 0.1 Rating Catalog Regulated outputs (#) 1 Features Accuracy (%) 2 PSRR @ 100 KHz (dB) 55 Dropout voltage (Vdo) (Typ) (mV) 1900 Operating temperature range (C) 0 to 125 open-in-new Find other Linear regulators (LDO)

Package | Pins | Size

TO-CAN (NDS) 2 969 mm² 38.94 x 24.89 open-in-new Find other Linear regulators (LDO)


  • Guaranteed 1% initial accuracy (A version)
  • 3 amp output current
  • Internal current and thermal limiting
  • 0.01 Ohm typical output impedance
  • 7.5V minimum input voltage
  • 30W power dissipation
  • P+ Product Enhancement tested

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The LM123 is a three-terminal positive regulator with a preset 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 limiting, 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 capacitor, 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 capacitance.

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 satisfactorily 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.

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Technical documentation

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Type Title Date
* Data sheet LM123/LM323A/LM323 3-Amp, 5-Volt Positive Regulator datasheet (Rev. B) Nov. 17, 2004
Technical article LDO basics: capacitor vs. capacitance Aug. 01, 2018
Technical article LDO Basics: Preventing reverse current Jul. 25, 2018
Technical article LDO basics: introduction to quiescent current Jun. 20, 2018
Technical article LDO basics: noise – part 1 Jun. 14, 2017
More literature Die D/S LM323 MWC 3-Amp, 5-Volt Positive Regulator Sep. 21, 2012

Design & development

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TO-3 (NDS) 2 View options

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