Texas Instruments LM317 Adjustable Positive Voltage Regulator, 1A, SOT-223

The Texas Instruments LM317EMP/NOPB is a highly versatile three-terminal adjustable positive voltage regulator, presented in a compact 4-pin SOT-223 surface-mount package. This regulator is exceptionally user-friendly, requiring only two external resistors to set the desired output voltage, making it ideal for both prototyping and production applications. It offers superior line and load regulation compared to standard fixed regulators, ensuring a stable and reliable output under varying conditions.

Beyond performance, the LM317 provides comprehensive overload protection typically only found in integrated circuits. This includes current limiting, thermal overload protection, and safe area protection. Crucially, all this protection circuitry remains fully operational even if the adjustment terminal is disconnected, enhancing the safety and robustness of your designs. For most installations, input and output capacitors are optional; an input bypass is only needed if the device is situated more than six inches from the input filter capacitors, while an output capacitor can be added to improve transient response.

A key feature is the adjustable output voltage, which can be precisely set from 1.2V to 37V, with a maximum output current of 1A. It accepts an input voltage range from 4.2V to 40V, with a typical dropout voltage of 2.25V. The regulator also boasts an impressive 80dB ripple rejection ratio, which can be further improved by bypassing the adjustment terminal—a feature difficult to achieve with standard three-terminal regulators. The output is short-circuit protected, and the device operates reliably across a temperature range of 0°C to 125°C.

With its combination of adjustability, robust protection, and high performance, the LM317 is a cornerstone component for a wide array of electronic power management tasks, from simple voltage references to complex power supply units.