LM342 Series 3-Terminal Positive Regulators
June 1989
LM342 Series
3-Terminal Positive Regulators
General Description
The LM342-XX series of three-terminal regulators is avail-
able with several fixed output voltages making them useful
in a wide range of applications One of these is local on card
regulation eliminating the distribution problems associated
with single point regulation The voltages available allow
these regulators to be used in logic systems instrumenta-
tion HiFi and other solid state electronic equipment Al-
though designed primarily as fixed voltage regulators these
devices can be used with external components to obtain
adjustable voltages and currents
The LM342-XX series is available in the plastic TO-202
package This package allows these regulators to deliver
over 0 25A if adequate heat sinking is provided Current lim-
iting is included to limit the peak output current to a safe
value Safe area protection for the output transistor is pro-
vided to limit internal power dissipation If internal power
dissipation becomes too high for the heat sinking provided
the thermal shutdown circuit takes over preventing the IC
from overheating
Considerable effort was expended to make the LM342-XX
series of regulators easy to use and minimize the number of
external components It is not necessary to bypass the
output although this does improve transient response Input
bypassing is needed only if the regulator is located far from
the filter capacitor of the power supply
For output voltage other than 5V 12V and 15V the LM117
series provides an output voltage range from 1 2V to 57V
Features
Y
Y
Y
Y
Y
Y
Y
Output current in excess of 0 25A
Internal thermal overload protection
No external components required
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-202 package
Special circuitry allows start-up even if output is pulled
to negative voltage (
g
supplies)
Voltage Range
LM342-5 0
LM342-12
LM342-15
5V
12V
15V
Schematic Diagram
TL H 10485 鈥?1
C
1995 National Semiconductor Corporation
TL H 10485
RRD-B30M115 Printed in U S A
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