November 1994
LM120 LM320
Series 3-Terminal Negative Regulators
General Description
The LM120 series are three-terminal negative regulators
with a fixed output voltage of b5V b12V and b15V and
up to 1 5A load current capability Where other voltages are
required the LM137 and LM137HV series provide an output
voltage range of b1 2V to b47V
The LM120 need only one external component a compen-
sation capacitor at the output making them easy to apply
Worst case guarantees on output voltage deviation due to
any combination of line load or temperature variation as-
sure satisfactory system operation
Exceptional effort has been made to make the LM120 Se-
ries immune to overload conditions The regulators have
current limiting which is independent of temperature com-
bined with thermal overload protection Internal current limit-
ing protects against momentary faults while thermal shut-
down prevents junction temperatures from exceeding safe
limits during prolonged overloads
Although primarily intended for fixed output voltage applica-
tions the LM120 Series may be programmed for higher out-
put voltages with a simple resistive divider The low quies-
cent drain current of the devices allows this technique to be
used with good regulation
Features
Y Preset output voltage error less than g3%
Y Preset current limit
Y Internal thermal shutdown
Y Operates with input-output voltage differential down to
1V
Y Excellent ripple rejection
Y Low temperature drift
Y Easily adjustable to higher output voltage
LM120 Series Packages and Power Capability
Device
Package
Rated
Power
Dissipation
Design
Load
Current
LM120 LM320 TO-3 (K)
20W
1 5A
TO-39 (H)
2W
0 5A
LM320
TO-220 (T)
15W
1 5A
LM320M
TO-202 (P)
7 5W
0 5A
Typical Applications
Dual Trimmed Supply
Fixed Regulator
TL H 7767–3
TL H 7767 – 2
Required if regulator is separated from filter capacitor by more than 3 For
value given capacitor must be solid tantalum 25 mF aluminum electrolytic
may be substituted
Required for stability For value given capacitor must be solid tantalum 25
mF aluminum electrolytic may substituted Values given may be increased
without limit
For output capacitance in excess of 100 mF a high current diode from
input to output (1N4001 etc ) will protect the regulator from momentary
input shorts
C1995 National Semiconductor Corporation TL H 7767
RRD-B30M115 Printed in U S A
