LM2936-50 National Semiconductor, LM2936-50 Datasheet - Page 5

• Manufacturer Part Number: LM2936-50
• Description: Ultra-Low Quiescent Current 5V Regulator
• Manufacturer: National Semiconductor

Typical Performance Characteristics
Line Transient Response
Load Transient Response
Applications Information
Unlike other PNP low dropout regulators, the LM2936 re-
mains fully operational to 40V. Owing to power dissipation
characteristics of the available packages, full output current
cannot be guaranteed for all combinations of ambient tem-
perature and input voltage. As an example, consider an
LM2936Z operating at 25˚C ambient. Using the formula for
maximum allowable power dissipation given in (Note 3) , we
find that P
tribution of the quiescent current to total power dissipation
the maximum input voltage (while still delivering 50 mA out-
put current) is 17.3V. The LM2936Z will go into thermal shut-
down if it attempts to deliver full output current with an input
voltage of more than 17.3V. Similarly, at 40V input and 25˚C
ambient the LM2936Z can deliver 18 mA maximum.
Under conditions of higher ambient temperatures, the volt-
age and current calculated in the previous examples will
drop. For instance, at the maximum ambient of 125˚C the
LM2936Z can only dissipate 128 mW, limiting the input volt-
age to 7.34V for a 50 mA load, or 3.5 mA output current for
a 40V input.
The junction to ambient thermal resistance
two distinct components: the junction to case thermal resis-
tance rating
rating
For the SO-8 and TO-252 surface mount packages the
rating can be improved by using the copper mounting pads
on the printed circuit board as a thermal conductive path to
extract heat from the package.
CA
. The relationship is defined as:
Dmax
JC
; and the case to ambient thermal resistance
= 641 mW at 25˚C. Including the small con-
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Output at
Voltage Extremes
Low Voltage Behavior
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=
rating has
JC
+
CA
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.
(Continued)
5
On the SO-8 package the four ground pins are thermally
connected to the backside of the die. Adding approximately
0.04 square inches of 2 oz. copper pad area to these four
pins will improve the
this extra pad are is placed directly beneath the package
there should not be any impact on board density.
On the TO-252 package the ground tab is thermally con-
nected to the backside of the die. Adding 1 square inch of 2
oz. copper pad area directly under the ground tab will im-
prove the
While the LM2936 has an internally set thermal shutdown
point of typically 150˚C, this is intended as a safety feature
only. Continuous operation near the thermal shutdown tem-
perature should be avoided as it may have a negative affect
on the life of the device.
While the LM2936 maintains regulation to 60V, it will not
withstand a short circuit above 40V because of safe operat-
ing area limitations in the internal PNP pass device. Above
60V the LM2936 will break down with catastrophic effects on
the regulator and possibly the load as well. Do not use this
device in a design where the input operating voltage may ex-
ceed 40V, or where transients are likely to exceed 60V.
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rating to approximately 50˚C/W.
Ripple Rejection
Output Impedance
JA
rating to approximately 110˚C/W. If
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