LM317 Adjustable Voltage Regulator TO-220

LM317 Adjustable Voltage Regulator TO-220 is a versatile three-terminal regulator capable of supplying a stable output voltage ranging from 1.25V to 37V at up to 1.5A. It is widely used in power supplies, battery chargers, LED drivers, and DIY electronics where adjustable voltage is required. With built-in current limiting, thermal shutdown, and safe area compensation, it offers reliable performance and protection.

Key Features:

• Adjustable Output Voltage: 1.25V to 37V range using external resistors.
• High Output Current: Provides up to 1.5A continuous current.
• Internal Protection: Built-in current limiting, thermal overload, and safe-area protection.
• TO-220 Package: Suitable for heat sinking in high-current applications.
• Easy Implementation: Requires only two external resistors for voltage adjustment.

Technical Specifications:

• Output Voltage Range: 1.25V to 37V (adjustable)
• Output Current: 1.5A max
• Line Regulation: 0.01%/V typical
• Load Regulation: 0.1% typical
• Dropout Voltage: 2 to 3V typical under full load
• Operating Temperature: 0°C to 125°C

Mechanical Specifications:

• Package Type: TO-220
• Number of Pins: 3
• Mounting Style: Through-hole
• Heatsink Compatible: Yes

Dimensions:

• Body Width: ~10.2mm
• Body Height: ~4.5mm
• Lead Pitch: 2.54mm (standard)
• Overall Height: ~15mm including leads

Pinout and Wiring:

• Pin 1 (Adjust): Connected to the voltage-setting resistor divider
• Pin 2 (Output): Regulated output voltage
• Pin 3 (Input): Unregulated DC input voltage
• Basic Setup: Use a voltage divider between V_OUT and ADJ to set output

Datasheet Reference:

• Search online for “LM317 voltage regulator datasheet by Texas Instruments or STMicroelectronics”

Applications:

• Adjustable Power Supplies: Regulate voltage for lab and field use
• Battery Chargers: Custom voltage-controlled charging circuits
• LED Drivers: Control brightness by setting drive voltage
• Arduino/Raspberry Pi Projects: Step down or regulate power sources
• Bench Power Tools: Ideal for voltage tweaking and testing circuits

Equivalent Models:

• LM317T: TO-220 version with same specs
• LM338: Higher current version (up to 5A)
• LT317: Drop-in replacement from Analog Devices
• AMS1117-ADJ: SMD adjustable regulator with lower current rating

Package Includes:

• 1 x LM317 Adjustable Voltage Regulator TO-220