Datasheet

P
D(max)
+
T
J
max * T
A
R
qJA
where:
T
J
max is the maximum allowable junction temperature
T
A
is the ambient temperature.
R
θJA
is the thermal resistance junction-to-ambient for the package, i.e., 27.9°C/W for the 28-terminal
PWP with no airflow.
P
D
+
ǒ
V
I
* V
O
Ǔ
I
O
TPS767D301-EP
SGLS327A –FEBRUARY 2006–REVISED APRIL 2010 www.ti.com
Regulator Protection
The TPS767D301-EP PMOS-pass transistor has a built-in back-gate diode that safely conducts reverse currents
when the input voltage drops below the output voltage (e.g., during power down). Current is conducted from the
output to the input and is not internally limited. When extended reverse voltage is anticipated, external limiting
may be appropriate.
The TPS767D301-EP also features internal current limiting and thermal protection. During normal operation, the
TPS767D301-EP limits output current to approximately 1.7 A. When current limiting engages, the output voltage
scales back linearly until the overcurrent condition ends. While current limiting is designed to prevent gross
device failure, care should be taken not to exceed the power dissipation ratings of the package. If the
temperature of the device exceeds 150°C (typ), thermal-protection circuitry shuts it down. Once the device has
cooled below 130°C (typ), regulator operation resumes.
Power Dissipation and Junction Temperature
Specified regulator operation is assured to a junction temperature of 125°C; the maximum junction temperature
should be restricted to 125°C under normal operating conditions. This restriction limits the power dissipation the
regulator can handle in any given application. To ensure the junction temperature is within acceptable limits,
calculate the maximum allowable dissipation, P
D(max)
, and the actual dissipation, P
D
, which must be less than or
equal to P
D(max)
.
The maximum power dissipation limit is determined using the following equation:
(3)
The regulator dissipation is calculated using:
(4)
Power dissipation resulting from quiescent current is negligible. Excessive power dissipation triggers the thermal
protection circuit.
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