Datasheet

LM9036
www.ti.com SNVS140E –AUGUST 2003–REVISED MARCH 2013
APPLICATIONS INFORMATION
Unlike other PNP low dropout regulators, the LM9036 remains fully operational to 40V. Owing to power
dissipation characteristics of the package, full output current cannot be ensured for all combinations of ambient
temperature and input voltage.
The junction to ambient thermal resistance θ
JA
rating has two distinct components: the junction to case thermal
resistance rating θ
JC
; and the case to ambient thermal resistance rating θ
CA
. The relationship is defined as: θ
JA
=
θ
JC
+ θ
CA
.
On the PFM package the ground tab is thermally connected to the backside of the die. Adding 1 square inch of 2
oz. copper pad area directly under the ground tab will improve the θ
JA
rating to approximately 50°C/W.
While the LM9036 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 temperature should be avoided as it may have a
negative affect on the life of the device.
Using the θ
JA
for a LM9036DT mounted on a circuit board as defined at, see
(1)
, and using the formula for
maximum allowable dissipation given in, see
(2)
, for an ambient temperature (T
A
) of +85°C, we find that P
DMAX
=
1.3W. Including the small contribution of the quiescent current I
Q
to the total power dissipation, the maximum
input voltage (while still delivering 50mA output current) is 29.5V. The LM9036DT will go into thermal shutdown
when attempting to deliver the full output current of 50mA, with an ambient temperature of +85°C, and the input
voltage is greater than 29.5V. Similarly, with an ambient temperature of 25°C the P
DMAX
= 2.5W, and the
LM9036DT can deliver the full output current of 50mA with an input voltage of up to 40V.
While the LM9036 maintains regulation to 55V, it will not withstand a short circuit above 40V because of safe
operating area limitations in the internal PNP pass device. Above 55V the LM9036 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 exceed 40V, or where transients are likely to exceed 55V.
(1) Typical θ
JA
with 1 square inch of 2oz copper pad area directly under the ground tab.
(2) The maximum power dissipation is a function of T
Jmax
, θ
JA
, and T
A
. The maximum allowable power dissipation at any ambient
temperature is P
D
= (T
Jmax
− T
A
)/θ
JA
. If this dissipation is exceeded, the die temperature will rise above 150°C and the LM9036 will go
into thermal shutdown.
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