LM317DRG

The LM317 is an adjustable three-terminal positive voltage regulator capable of supplying more than 100mA over an output voltage range of 1.2V to 37V. The device is easy to use, requiring only two external resistors to set the output voltage. It integrates internal current limiting, thermal shutdown, and safe operating area compensation, providing reliable protection. This regulator is suitable for a variety of applications, including local regulation and on-board regulation. It can also be used to build programmable regulators, or as a precision current regulator by connecting a fixed resistor between the adjustment pin and the output pin. The output voltage is given by the formula Vout = 1.25V × (1 + R2/R1) + IAdj × R2, where IAdj is typically about 50 μA and can be neglected in most applications. For optimum performance, it is recommended to mount programming resistor R1 as close to the regulator as possible, and to locate the ground point of R2 near the load ground. A 0.1 μF ceramic capacitor or 1 μF tantalum capacitor is recommended as the input bypass capacitor (Cin). Adding a bypass capacitor (Cadj) from the adjustment pin to ground improves ripple rejection; for example, in a 10V application, a 10 μF capacitor can improve ripple rejection by approximately 15dB at 120Hz. Although the LM317 remains stable without an output capacitor, using a 1.0 μF tantalum capacitor or 25 μF aluminum electrolytic capacitor as the output capacitor (Co) ensures stability and prevents abnormal oscillation. When the output voltage exceeds 25V or large capacitors are used (Co > 25 μF, Cadj > 10 μF), protection diodes are recommended to prevent the capacitors from discharging into the regulator under low-current conditions. Hanxin Semiconductor products are not authorized for use in life support or similar applications, and Hanxin Semiconductor assumes no liability for consequences arising from such use.

Key features

• Output current exceeding 100 mA
• Output voltage adjustable from 1.2V to 37V
• Internal thermal overload protection
• Temperature-independent internal short-circuit current limiting
• Output transistor safe operating area compensation
• No need to stock multiple fixed voltages