TL/H/7767
L
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
b
5V,
b
12V, and
b
15V, and
up to 1.5A load current capability. Where other voltages are
required, the LM137 and LM137HV series provide an output
voltage range of
b
1.2V to
b
47V.
The LM120 need only one external componentDa 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
g
3%
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
Rated
Power
Dissipation
Design
Load
Current
Device
Package
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
TL/H/7767–3
Fixed Regulator
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
m
F aluminum electrolytic
may be substituted.
2
Required for stability. For value given, capacitor must be solid tantalum. 25
m
F aluminum electrolytic may substituted. Values given may be increased
without limit.
For output capacitance in excess of 100
m
F, a high current diode from
input to output (1N4001, etc.) will protect the regulator from momentary
input shorts.
C
1995 National Semiconductor Corporation
RRD-B30M115/Printed in U. S. A.