lm7812 pdf

LM7812
Series Voltage Regulators
General Description
The LM7812series of three terminal regulators is available
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, instrumentation,
HiFi, and other solid state electronic equipment. Although
designed primarily as fixed voltage regulators these
devices can be used with external components to obtain adjustable
voltages and currents.
The LM78XX series is available in an aluminum TO-3 package
which will allow over 1.0A load current if adequate heat
sinking is provided. Current limiting is included to limit the
peak output current to a safe value. Safe area protection for
the output transistor is provided 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 expanded to make the LM78XX 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.