Adjustable Voltage Regulator Texas Instruments LM317AEMP, output 1.2–37 V, SOT-223 package

The Texas Instruments LM317AEMP is an adjustable linear voltage regulator in a compact SOT-223 package that provides a stable DC output adjustable from 1.2 V to 37 V. Designed for user-defined regulated voltages via external resistor networks, this regulator suits power supplies for bench equipment, embedded systems, and small electronic devices where space is limited. The device is intended for linear regulation applications requiring a simple, reliable solution for obtaining a specific output voltage with minimal external components.

Advantages

The LM317AEMP offers a wide adjustable output range and straightforward set-up using two external resistors to define the output voltage. Its SOT-223 package provides a compact physical footprint while allowing adequate thermal performance for low- to moderate-power applications. The device requires few external components, is widely supported in reference designs, and is compatible with common protection and decoupling practices used in power regulation circuits.

Suitable for

• Adjustable bench power supplies and laboratory regulators
• Embedded systems and microcontroller-based projects
• Prototype boards and development systems requiring a regulated DC rail
• Small consumer electronics and instrumentation with low to moderate current needs

Key specifications

• Output voltage range: 1.2 V to 37 V adjustable
• Device type: Linear adjustable regulator
• Package: SOT-223 compact surface-mount package
• Adjustment method: External resistor divider sets output voltage
• Typical application power level: low to moderate currents (dependent on thermal conditions)

How to use

Configure the LM317AEMP by connecting an appropriate resistor between the output and adjust pins and a second resistor from the adjust pin to ground to set the desired output voltage according to the standard regulator equation. Include input and output capacitors as recommended for stability and transient response; ensure the input voltage is sufficiently higher than the intended output to accommodate dropout and regulation headroom. Mount the SOT-223 package on a PCB with adequate copper area or a small heatsink if higher dissipation is anticipated. Follow standard layout practices for power regulators: short traces for the adjust network and decoupling components, and proper grounding to minimize noise.

Recommendations

For reliable operation, provide input voltage at least a few volts above the desired output to account for dropout and ensure correct thermal dissipation. Use low-ESR capacitors on the input and output as indicated in application notes, keep the adjust resistors low enough to limit noise but high enough to avoid excessive quiescent current, and verify temperature-rise on the PCB under expected load conditions. Consult the manufacturer's application information for detailed stability and protection guidance.