The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to. RθJC(bot) Junction-to-case (bottom) thermal resistance NA 0.1 4.2 1.1 °C/W. 5 LM317 www.ti.com SLVS044X –SEPTEMBER 1997–REVISED SEPTEMBER 2016 Product Folder Links: LM317.

The output voltage from the LM317 and LM338 is set using two ( R1 and R2) with their values chosen according to the following equation: V OUT = 1.25 * ( 1 + R2/R1 ) REUK LM317/LM338 Voltage CalculatorBelow is our automated voltage calculator for the LM317 and LM338 regulators. Simply enter your target output voltage Vout and chosen value for R1 (100 to 1000 Ohms), click Calculate, and the required value of R2 will be displayed. Vout: Target Output Voltage 1.5 to 37.0 Volts R1: R1 Resistor Value 100-1000 Ohms R2: Click Calculate to display the calculated R2 value here. The results given above can be used to put together a voltage regulator, but the calculated value of R2 will not be a standard/stock resistor value.

Since the accuracy of the voltage regulator itself will be up to 5% out, and resistor values are not exact, it is common to use a (aka variable resistor or trim pot) for some or all of R2. This enables the output voltage to be manually fine-tuned to provide the exact voltage required. Enter values of R1 and R2 below to calculate the corresponding value of Vout.

R1: R1 Resistor Value 100-1000 Ohms R2: R2 Resistor Value Vout: Click Calculate to display the calculated Vout value here. Output Voltage Tables for Stock R1 and R2 Values Where a very accurate voltage is not required, it is much easier to use standard (stock) resistors to put together an LM317 or LM338 voltage regulator.

Below are tables of output voltages for different combinations of the most commonly found resistors.