1.5-A, 40-V, adjustable linear voltage regulator

The LM317 is an adjustable three-pin,

positive-voltage regulator capable of supplying more than 1.5A over an output

voltage range of 1.25V to 37V. The device requires only two external resistors to

set the output voltage. The device features a typical line regulation of 0.01% and

typical load regulation of 0.1%. The LM317 includes current limiting, thermal

overload protection, and safe operating area protection. Overload protection remains

functional even if the ADJUST pin is disconnected.

Typically, no capacitors are needed

unless the device is situated more than 6 inches from the input filter capacitors.

In that case, an input bypass is needed. Add an optional output capacitor to improve

transient response. Bypass the adjustment pin to achieve very high ripple rejection

ratios that are difficult to achieve with standard 3-pin regulators.

The regulator is floating and

detects only the input-to-output differential voltage. Thus, supplies of several

hundred volts are regulated as long as the maximum input-to-output differential is

not exceeded. That is, avoid short-circuiting the output.

By connecting a fixed resistor between

the adjustment pin and output, the LM317 is also able to be used as a precision

current regulator. Supplies with electronic shutdown are achieved by clamping the

adjustment terminal to ground, which programs the output to 1.25V where most loads

draw little current.