The LM117 and LM317-N series of adjustable 3-pin positive voltage regulators are capable
of supplying in excess of 1.5 A over a 1.25-V to 37-V output range and a wide temperature range.
They are exceptionally easy to use and require only two external resistors to set the output
voltage. Further, both line and load regulation are better than standard fixed
The LM117 and LM317-N offer full overload protection such as current limit, thermal
overload protection and safe area protection. All overload protection circuitry remains fully
functional even if the adjustment terminal is disconnected.
Typically, no capacitors are needed unless the device is situated 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 that are difficult to achieve with standard 3-terminal
Because the regulator is and detects 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. That is, avoid short-circuiting the
By connecting a fixed resistor between the adjustment pin and output, the LM117 and
LM317-N can be also used as a precision current regulator. Supplies with electronic shutdown can be
achieved by clamping the adjustment terminal to ground, which programs the output to 1.25 V where
most loads draw little current.
For applications requiring greater output current, see data sheets for LM150 series (3
A), SNVS772, and LM138 series (5 A),
SNVS771. For the negative complement, see LM137 (SNVS778) series data sheet.
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