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Datasheet del c.i. LM317

3-Terminal Adjustable Regulator
General Description

LM117/LM317A/LM317 3-Terminal Adjustable Regulator
May 1996

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 resistorsto 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 overloadprotection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment ter- minal 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 canbe bypassed to achieve very high ripple rejection ratios which are difficult to achieve with stan- dard 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 volt- age, supplies of several hundred volts can be regulated as long as the maximum inputto output differential is not ex- ceeded, i.e., avoid short-circuiting the output.
Also, it makes an especially simple adjustable switching reg- ulator, 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. Sup- plies with electronic shutdown can be achieved by clamping


1.2V – 25V Adjustable Regulator

the adjustment terminal to ground which programs the out- put 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 neg- ative complement, see LM137 series data sheet.
LM117 Series Packages and Power Capability

Part NumberSuffix | Package |Rated Power Dissipation | Design Load Current |
K | TO-3 | 20W | 1.5A |
H | TO-39 | 2W | 0.5A |
T | TO-220 | 20W | 1.5A |
E | LCC | 2W | 0.5A |
S | TO-263 | 4W | 1.5A |

Y Guaranteed 1% output voltage tolerance
Y Guaranteed max. 0.01%/V line regulation
Y Guaranteed max. 0.3% load regulation
Y Guaranteed 1.5A output current
Y Adjustableoutput down to 1.2V
Y Current limit constant with temperature
Y Pa Product Enhancement tested
Y 80 dB ripple rejection
Y Output is short-circuit protected

Digitally Selected Outputs

Full output current not available at high input-output voltages

TL/H/9063 – 1

*Needed if device is more than 6 inches from filter capacitors.
†Optional—improves transient response. Output capacitorsin the range of
1 mF to 1000 mF of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients.
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††VOUT e 1.25V 1 a R1 a IADJ(R2)

*Sets maximum VOUT

TL/H/9063 – 2

C1996 National Semiconductor Corporation


RRD-B30M56/Printed in U. S. A. http://www.national.comAbsolute Maximum Ratings (Note 1) Operating Temperature RangeIf Military/Aerospace specified devices are required, LM117 b55°C s TJ s a150°C please contact the National Semiconductor Sales LM317A b40°C s TJ s a125°C Office/Distributors for availability...
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