LM317 Adjustable Voltage Regulator TO-92

LM317 Adjustable Voltage Regulator TO-92 is a versatile and highly popular linear voltage regulator designed to supply a precisely controlled output voltage across a broad range. This three-terminal positive regulator offers an adjustable output voltage from 1.25 V up to 37 V. Consequently, design engineers widely choose the compact TO-92 package when space is limited and output current demand is moderate. Unlike fixed voltage regulators, you only need two external resistors to set the output voltage, providing exceptional flexibility. Furthermore, the LM317 inherently includes internal current limiting, thermal shutdown, and safe operating area protection, reliably protecting the device from damage under overload conditions. Therefore, rely on the LM317 in the TO-92 package to build stable, compact, and customized power supplies for various electronic projects.

Key Features:

• Adjustable Output Voltage: The regulator offers a continuously adjustable output voltage range from 1.25 V to 37 V.
• Integrated Protection: Includes built-in thermal overload protection and short-circuit current limiting to maximize component lifespan and safety.
• Low Noise Operation: Produces a relatively low output noise level, making it suitable for sensitive analog and audio applications.
• High Line Regulation: The LM317 typically provides line regulation of better than 0.01% per volt of input change, maintaining output stability.
• Compact Package: The small, plastic TO-92 package minimizes the physical footprint on space-constrained printed circuit boards (PCBs).

Technical Specifications:

• Output Voltage Range (V_OUT): 1.25 V to 37 V
• Input Voltage Max (V_IN): 40 V (Absolute maximum)
• Maximum Output Current (I_MAX): 100 mA (Typical for TO-92 package without heat sinking)
• Reference Voltage (V_REF): 1.25 V (Between ADJ and OUT pins)
• Line Regulation: Typically 0.01% / V
• Load Regulation: Typically 0.1%
• Minimum Load Current (I_L): ≈ 3.5 mA to ensure regulation
• Operating Junction Temperature: 0°C to +125°C (Commercial Grade)

Mechanical Specifications:

• Package Style: TO-92 (Transistor Outline)
• Pin Material: Tinned Copper/Steel
• Mounting: Through-Hole Technology (THT)
• Construction: Plastic Encapsulation

Dimensions:

• Body Height: ≈ 4.3 mm (Excluding leads)
• Body Diameter/Width: ≈ 4.1 mm (Cylindrical or D-shaped body)
• Lead Pitch (E): 1.27 mm (Standard TO-92 spacing)
• Overall Height (H): ≈ 8.8 mm (Max)
• Weight: ≈ 0.2 g (Extremely lightweight)

Pinout and Wiring:

• Pin 1 (Adjustment, ADJ): Connect this pin to the center tap of the external resistor voltage divider network to set the output voltage.
• Pin 2 (Output, V_OUT): This pin provides the regulated DC output voltage to your load circuit.
• Pin 3 (Input, V_IN): Apply the unregulated DC input voltage here (V_IN must be ≥ V_OUT + 3 V).
• Wiring Note: You must always place a small capacitor (e.g., 0.1 μF ceramic) on the input and a larger one (e.g., 1 μF tantalum or electrolytic) on the output to ensure stability and smooth operation.

Datasheet Reference:

• Download LM317 Datasheet

Commonly Used in:

• Hobby Electronics: A staple in DIY projects, breadboards, and Arduino-based circuits requiring variable power.
• Low-Power Sensors: Providing a precise, stable voltage source for analog sensors and instrumentation.
• LED Current Drivers: Engineers frequently use the LM317 in a constant current configuration to drive power LEDs efficiently.

Applications:

• Bench Power Supplies: Forming the control element for small, adjustable regulated power supplies.
• Battery Chargers: Building custom constant-voltage or constant-current battery charging circuits.
• Variable Voltage Sources: Creating on-board power supplies where the final output voltage must be trimmed during assembly.
• Pre-Regulation Stages: Providing a regulated voltage to subsequent fixed regulators, minimizing power dissipation.

Equivalent Models:

• LM317LZ (ON Semi): The same part number suffix often used by ON Semiconductor for the TO-92 package version.
• L78S10CV (STMicro): However, this is a fixed 10V regulator, which is only an equivalent if you specifically require 10V output (LM317 offers more flexibility).
• TL317 (Various Manufacturers): A pin-compatible low-noise version often offered as an enhanced drop-in replacement.

Package Includes:

• 1 x LM317 Adjustable Voltage Regulator IC (TO-92)