Datasheet
SLVS323B − FEBRUARY 2001 − REVISED JANUARY 2007
9
APPLICATION INFORMATION
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:
P
D(max)
+
T
J
max * T
A
R
qJA
Where:
T
J
max is the maximum allowable junction temperature.
R
θJA
is the thermal resistance junction-to-ambient for the package, see the dissipation rating table.
T
A
is the ambient temperature.
The regulator dissipation is calculated using:
P
D
+
ǒ
V
I
* V
O
Ǔ
I
O
Power dissipation resulting from quiescent current is negligible. Excessive power dissipation will trigger the
thermal protection circuit.
regulator protection
The TPS76201 PMOS-pass transistor has a built-in back diode that conducts reverse current 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. If extended reverse voltage operation is anticipated, external limiting might
be appropriate.
The TPS76201 features internal current limiting and thermal protection. During normal operation, the
TPS76201 limits output current to approximately 350 mA. 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 approximately 165°C, thermal-protection circuitry shuts it down. Once the
device has cooled down to below approximately 140°C, regulator operation resumes.
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