LM317L

3-Terminal Adjustable Regulator

General Description

The LM317L is an adjustable 3-terminal positive voltage

regulator capable of supplying 100mA over a 1.2V to 37V

output range. It is exceptionally easy to use and requires

only two external resistors to set the output voltage. Further,

both line and load regulation are better than standard fixed

regulators. Also, the LM317L is available packaged in a stan-

dard TO-92 transistor package which is easy to use.

In addition to higher performance than fixed regulators, the

LM317L offers full overload protection. Included on the chip

are current limit, thermal overload protection and safe area

protection. All overload protection circuitry remains fully func-

tional even if the adjustment terminal is disconnected.

Normally, no capacitors are needed unless the device is situ-

ated more than 6 inches from the input filter capacitors in

which case an input bypass is needed. An optional output

capacitor can be added to improve transient response. The

adjustment terminal can be bypassed to achieve very high

ripple rejection ratios which are difficult to achieve with stan-

dard 3-terminal regulators.

Besides replacing fixed regulators, the LM317L is useful in a

wide variety of other applications. Since the regulator is

“floating” and sees only the input-to-output differential volt-

age, supplies of several hundred volts can be regulated as

long as the maximum input-to-output differential is not ex-

ceeded.

Also, it makes an especially simple adjustable switching

regulator, a programmable output regulator, or by connecting

a fixed resistor between the adjustment and output, the

LM317L can be used as a precision current regulator. Sup-

plies with electronic shutdown can be achieved by clamping

the adjustment terminal to ground which programs the out-

put to 1.2V where most loads draw little current.

The LM317L is available in a standard TO-92 transistor

package, the SO-8 package, and 6-Bump micro SMD pack-

age. The LM317L is rated for operation over a −25˚C to

125˚C range.

Features

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Adjustable output down to 1.2V

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Guaranteed 100 mA output current

n

Line regulation typically 0.01%V

n

Load regulation typically 0.1%

n

Current limit constant with temperature

n

Eliminates the need to stock many voltages

n

Standard 3-lead transistor package

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80 dB ripple rejection

n

Available in TO-92, SO-8, or 6-Bump micro SMD

package

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Output is short circuit protected

n

See AN-1112 for micro SMD considerations

Connection Diagrams

TO-92 Plastic package

DS009064-4

8-Pin SOIC

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Top View

March 2000

© 2000 National Semiconductor Corporation

DS009064

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