LM317 Adjustable Voltage Regulator TO-252

LM317 Adjustable Voltage Regulator in the TO-252 (DPAK) package delivers reliable, continuously adjustable output voltage from 1.25V to 37V. As a highly versatile positive voltage regulator, it requires only two external resistors to set the desired output level. The TO-252 package provides a surface-mount form factor, making it an excellent choice for compact electronic designs and power management circuits where board space is limited. This regulator capably supplies over 1.5A of load current and features built-in current limiting and thermal shutdown protection, allowing you to design stable, safe, and efficient power supplies for various projects, including microcontrollers, small motors, and LED drivers.

Key Features:

• Adjustable Output: You can effortlessly set the output voltage across a wide range, from 1.25V to 37V, using just two external resistors.
• High Current Capability: The device reliably sources over 1.5A of load current, accommodating most general-purpose applications.
• Built-in Protection: Features include current limit, thermal overload protection, and safe operating area compensation, protecting both the regulator and the load.
• Excellent Line and Load Regulation: Maintains a stable output voltage despite fluctuations in the input voltage or changes in the load current.
• Surface Mount Package: The TO-252 (DPAK) form factor is optimized for automated assembly and compact Printed Circuit Board (PCB) layouts.

Technical Specifications:

• Input Voltage Range (V_in): 3 V to 40 V
• Output Voltage Range (V_out): 1.25 V to 37 V
• Output Current (I_out): ≥ 1.5 A (Typical)
• Line Regulation: ≈ 0.01% / V (Typical)
• Minimum Load Current: ≈ 10 mA
• Dropout Voltage: ≈ 2 V (at I_out = 1.5 A)

Mechanical Specifications:

• Package Type: TO-252 (DPAK, Surface Mount)
• Number of Pins: 3
• Thermal Resistance: Requires appropriate PCB copper area for heat dissipation due to high current handling.
• Operating Temperature Range (T_j): -40°C to +125°C

Dimensions:

• Body Length: ≈ 6.7 mm
• Body Width: ≈ 6.1 mm
• Height: ≈ 2.3 mm
• Weight: ≈ 0.35 g

Pinout and Wiring:

• Pin 1 (ADJ/Adjustment): Connects to the junction of the resistor divider (R1 and R2). This pin sets the output voltage.
• Pin 2 (V_out/Output): The regulated output voltage point, connected to the copper tab/heat sink area on the PCB.
• Pin 3 (V_in/Input): Connects to the unregulated DC input voltage source.
• Basic Setup: You must connect the V_out pin to the load, V_in to the power source, and connect R1 (120Ω or 240Ω fixed resistor) and R2 (variable or fixed resistor) between ADJ and ground to set V_out.

Datasheet Reference:

• Download LM317 TO-252 Datasheet

Commonly Used in:

• Power Supply Design: Serving as the core component in laboratory adjustable power supplies and breadboard power modules.
• LED Lighting Circuits: Used to create constant current drivers for high-power LEDs.
• Automotive Electronics: Providing stable power rails that can tolerate the fluctuating car battery voltage.

Applications:

• Regulated DC Power Supplies: Building robust, custom voltage sources for electronic prototypes.
• Battery Chargers: Creating constant voltage/constant current (CV/CC) circuits for lithium and lead-acid batteries.
• High-Efficiency Pre-Regulators: Used to stabilize voltage before a linear or switching regulator for improved system efficiency.

Equivalent Models:

• LM317T (TO-220): The through-hole version, offering the same electrical specifications but a bulkier package.
• LM117/LM217: Higher reliability versions rated for wider military and industrial temperature ranges.
• LM338: A higher current adjustable regulator (up to 5A) for more power-intensive applications.

Package Includes:

• 1 x LM317 Adjustable Voltage Regulator (TO-252 DPAK)