July 2004
LM117/LM317A/LM317
3-Terminal Adjustable Regulator
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.
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.
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.
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 ter-
minal is disconnected.
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
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 stan-
dard 3-terminal regulators.
n Current limit constant with temperature
n P+ Product Enhancement tested
n 80 dB ripple rejection
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-
n Output is short-circuit protected
LM117 Series Packages
Typical Applications
Part Number
Suffix
Design
Load
Current
1.5A
1.2V–25V Adjustable Regulator
Package
K
H
TO-3
TO-39
0.5A
1.5A
T
TO-220
LCC
E
0.5A
1.5A
S
TO-263
SOT-223
TO-252
EMP
MDT
1A
0.5A
00906301
SOT-223 vs. D-Pak (TO-252)
Packages
Full output current not available at high input-output voltages
*
Needed if device is more than 6 inches from filter capacitors.
†
Optional — improves transient response. Output capacitors in the range
of 1µF to 1000µF of aluminum or tantalum electrolytic are commonly used
to provide improved output impedance and rejection of transients.
00906354
Scale 1:1
© 2004 National Semiconductor Corporation
DS009063
www.national.com
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