LM323K - 5V, 3A Positive Voltage Regulator

Overview

The LM323K is a robust three-terminal positive voltage regulator designed to deliver a fixed 5V output with exceptional load driving capability of up to 3A. This component represents a significant advancement in voltage regulation technology, employing innovative circuit design and manufacturing techniques to maintain precise voltage regulation even under high current demands. The device is particularly suitable for applications requiring stable power delivery in demanding environments.

As part of the LM123 family, the LM323K builds upon proven regulator architecture while incorporating modern improvements. The regulator features internal current limiting, thermal shutdown protection, and safe-area compensation - making it highly resilient against overload conditions. Its design emphasizes reliability and performance consistency across varying operating conditions.

Key Features

• Fixed 5V Output: Precision voltage reference provides stable 5V ±1% (A version) output voltage
• High Current Capacity: Capable of delivering up to 3A continuous output current
• Excellent Regulation: Typically 0.01%/V line regulation and 0.3% load regulation
• Thermal Protection: Built-in thermal shutdown prevents damage from overheating
• Current Limiting: Internal current limiting protects against short circuits
• Wide Operating Range: Input voltage range from 7.5V to 20V
• Low Dropout Voltage: 2V maximum dropout voltage at 3A output
• Robust Construction: Available in TO-3 metal package for superior thermal performance

Applications

The LM323K is designed for a wide range of power supply applications, particularly where stable, high-current 5V power is required:

Power Supply Systems

• Bench power supplies
• Switching regulator post-regulation
• Distributed power systems

Industrial Equipment

• Factory automation controllers
• Motor control circuits
• PLC power modules

Computer Systems

• Motherboard voltage regulation
• Peripheral device power
• Expansion card voltage conversion

Consumer Electronics

• High-power audio amplifiers
• Gaming console power circuits
• Set-top box power supplies

Electrical Characteristics

The following specifications are typical at 25°C unless otherwise noted:

Absolute Maximum Ratings

• Input Voltage: 20V
• Power Dissipation: Internally Limited
• Operating Junction Temperature Range: -40°C to +125°C
• Storage Temperature Range: -65°C to +150°C
• Lead Temperature (Soldering, 10 sec): 300°C

Electrical Specifications

• Output Voltage: 4.95V to 5.05V (A version, 1% tolerance)
• Line Regulation: 10mV (7.5V ≤ V_IN ≤ 20V)
• Load Regulation: 15mV (0 ≤ I_OUT ≤ 3A)
• Quiescent Current: 10mA typical
• Dropout Voltage: 2V max at 3A
• Output Noise Voltage: 40μV typical (10Hz to 100kHz)
• Ripple Rejection: 74dB typical at 120Hz
• Short Circuit Current: 3.5A typical
• Thermal Resistance: Junction-Case 3°C/W

Package Information

The LM323K is available in a robust TO-3 metal can package, offering excellent thermal performance for high-current applications:

TO-3 Package Dimensions

• Package Type: 2-lead metal can
• Height: 9.65mm (0.380 inches) max
• Diameter: 18.67mm (0.735 inches) max
• Lead Diameter: 1.32mm (0.052 inches)
• Mounting Hole Diameter: 3.96mm (0.156 inches)
• Weight: 10.5 grams typical

Thermal Considerations

The TO-3 package provides excellent thermal characteristics, but proper heat sinking is essential for reliable operation at maximum current:

• Maximum junction temperature: 125°C
• Thermal resistance, junction-to-case: 3°C/W
• Thermal resistance, junction-to-ambient: 35°C/W (without heatsink)
• Recommended heatsink thermal resistance: ≤5°C/W for full 3A operation

Pin Configuration

• Pin 1 (Input): Unregulated input voltage (7.5V to 20V)
• Pin 2 (Ground): Common ground reference
• Case (Output): Regulated 5V output (connected to metal can)

Reliability and Compliance

The LM323K is designed and tested to meet stringent quality and reliability standards:

• MIL-STD-883 compliant screening available
• ESD protection: 2kV Human Body Model
• Operating life: 100,000 hours MTBF at 50°C
• RoHS compliant version available

Design Considerations

For optimal performance when using the LM323K:

• Input capacitors (0.33μF minimum) should be placed close to the regulator
• Output capacitors (0.1μF minimum) improve transient response
• For high current applications, use wide PCB traces or bus bars
• Ensure proper heat sinking for continuous high-current operation
• Consider derating at elevated ambient temperatures