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(3-Terminal Adjustable Regulator)

General Description

The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output 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 regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and

handled. In addition to higher performance than fixed regulators, the

LM117 series offers full overload protection available only in IC's. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal

is disconnected. Normally, 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 which are difficult to achieve with standard 3-terminal regulators.

Besides replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the regulator is “floating” 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, i.e., avoid short-circuiting the output. Also, it makes an especially simple adjustable switching regulator,

a programmable output regulator, or by connecting a fixed resistor between the adjustment pin and output, the LM117 can be 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 1.2V where most loads draw little current. For applications requiring greater output current, see LM150

series (3A) and LM138 series (5A) data sheets. For the negative complement, see LM137 series data sheet.


· Guaranteed 1% output voltage tolerance (LM317A)

· Guaranteed max. 0.01%/V line regulation (LM317A)

· Guaranteed 1.5A output current

· Adjustable output down to 1.2V

· Current limit constant with temperature

· P+ Product Enhancement tested

· 80 dB ripple rejection

· Output is short-circuit protected



Vout range 1.25V - 37V
Vin - Vout difference 3V - 40V
Operation ambient temperature 0 - 125°C
Output Imax <1.5A
Minimum Load Currentmax 10mA




Circuit of Power Supply using LM317