LM317L 3-Terminal Adjustable Regulator
September 14, 2010
LM317L
3-Terminal Adjustable Regulator
General Description
The LM317L is an adjustable 3-terminal positive voltage reg-
ulator 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 standard 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 sit-
uated more than 6 inches from the input filter capacitors in
which case an input bypass is needed. An optional output ca-
pacitor 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 “float-
ing” and sees only the input-to-output differential voltage,
supplies of several hundred volts can be regulated as long as
the maximum input-to-output differential is not exceeded.
Also, it makes an especially simple adjustable switching reg-
ulator, 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. Supplies with
electronic shutdown can be achieved by clamping the adjust-
ment terminal to ground which programs the output to 1.2V
where most loads draw little current.
The LM317L is available in a standard TO-92 transistor pack-
age, the SO-8 package, and 6-Bump micro SMD package.
The LM317L is rated for operation over a −40°C to 125°C
range.
Features
■
■
■
■
■
■
■
■
■
■
■
Adjustable output down to 1.2V
Guaranteed 100mA output current
Line regulation typically 0.01%V
Load regulation typically 0.1%
Current limit constant with temperature
Eliminates the need to stock many voltages
Standard 3-lead transistor package
80dB ripple rejection
Available in TO-92, SO-8, or 6-Bump micro SMD package
Output is short circuit protected
See AN-1112 for micro SMD considerations
Connection Diagrams
TO-92 Plastic package
8-Pin SOIC
906405
906404
Top View
© 2010 National Semiconductor Corporation
9064
www.national.com
TI [ TEXAS INSTRUMENTS ]
