National LM117 LM317A LM317 User Guide

/L /L -T rm in l A ju ta le la to

April 2007

LM117/LM317A/LM317 3-Terminal Adjustable Regulator

the maximum input to output differential is not exceeded, i.e.,

General Description

avoid short-circuiting the output.

The LM117 series of adjustable 3-terminal positive voltage

Also, it makes an especially simple adjustable switching reg-

regulators is capable of supplying in excess of 1.5A over a

ulator, a programmable output regulator, or by connecting a

1.2V to 37V output range. They are exceptionally easy to use

fixed resistor between the adjustment pin and output, the

and require only two external resistors to set the output volt-

LM117 can be used as a precision current regulator. Supplies

age. Further, both line and load regulation are better than

with electronic shutdown can be achieved by clamping the

standard fixed regulators. Also, the LM117 is packaged in

adjustment terminal to ground which programs the output to

standard transistor packages which are easily mounted and

1.2V where most loads draw little current.

handled.

For applications requiring greater output current, see LM150

In addition to higher performance than fixed regulators, the

series (3A) and LM138 series (5A) data sheets. For the neg-

LM117 series offers full overload protection available only in

ative complement, see LM137 series data sheet.

IC's. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection

Features

circuitry remains fully functional even if the adjustment termi-

nal is disconnected. Guaranteed 1% output voltage tolerance (LM317A) Normally, no capacitors are needed unless the device is sit- Guaranteed max. 0.01%/V line regulation (LM317A)

uated more than 6 inches from the input filter capacitors in Guaranteed max. 0.3% load regulation (LM117) which case an input bypass is needed. An optional output ca-

Guaranteed 1.5A output current

pacitor can be added to improve transient response. The

Adjustable output down to 1.2V

adjustment terminal can be bypassed to achieve very high

ripple rejection ratios which are difficult to achieve with stan- Current limit constant with temperature

dard 3-terminal regulators. P+ Product Enhancement tested Besides replacing fixed regulators, the LM117 is useful in a 80 d B ripple rejection wide variety of other applications. Since the regulator is “float-

Output is short-circuit protected

ing” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as

LM117/LM317A/LM317 Package Options

Typical Applications

Part Output

Suffix Package

1.2V–25V Adjustable Regulator Number Current LM117, LM317 TO-3 1.5A LM317 TO-220 1.5A LM317 TO-263 1.5A LM317A, LM317 EMP SOT-223 1.0A LM117, LM317A, LM317 TO-39 0.5A LM117 LCC 0.5A LM317A, LM317 MDT TO-252 0.5A

SOT-223 vs. TO-252 (D-Pak) Packages

Full output current not available at high input-output voltages *Needed if device is more than 6 inches from filter capacitors. †Optional—improves transient response. Output capacitors in the range of 1μF to 1000μF of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients.

Scale 1:1

© 2007 National Semiconductor Corporation www.national.com