LM317 Regulator

LM317 Regulator - LM117/LM317A/LM317 3-Terminal Adjustable Regulator August 1999 LM117/LM317A/LM317 3-Terminal Adjustable Regulator General

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LM117/LM317A/LM317 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 termi- nal 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 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 input to output differential is not ex- ceeded, 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. 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. 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. Features n Guaranteed 1% output voltage tolerance (LM317A) n Guaranteed max. 0.01%/V line regulation (LM317A) n Guaranteed max. 0.3% load regulation (LM117) n Guaranteed 1.5A output current n Adjustable output down to 1.2V n Current limit constant with temperature n P + Product Enhancement tested n 80 dB ripple rejection n Output is short-circuit protected Typical Applications LM117 Series Packages Part Number Design Suffix Package Load Current K TO-3 1.5A H TO-39 0.5A T TO-220 1.5A E LCC 0.5A S TO-263 1.5A EMP SOT-223 1A MDT TO-252 0.5A SOT-223 vs D-Pak (TO-252) Packages 1.2V–25V Adjustable Regulator DS009063-1 Full output current not available at high input-output voltages * Needed if device is more than 6 inches from filter capacitors.
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This note was uploaded on 10/19/2008 for the course ECE 2B taught by Professor York during the Winter '07 term at UCSB.

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LM317 Regulator - LM117/LM317A/LM317 3-Terminal Adjustable Regulator August 1999 LM117/LM317A/LM317 3-Terminal Adjustable Regulator General

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