TL/H/7767
LM120/LM320 Series 3-Terminal Negative Regulators
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 componentÐa 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 Design
Device Package Power Load
Dissipation 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
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 mF aluminum electrolytic
may be substituted.
²
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.
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.