Datasheet

TPS76425, TPS76427, TPS76428, TPS76430, TPS76433
LOW-POWER LOW-NOISE 150-mA LOW-DROPOUT LINEAR REGULATORS
SLVS180B – MARCH 1999 – REVISED MAY 2001
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
power dissipation and junction temperature
Specified regulator operation is assured to a junction temperature of 125°C; the maximum junction temperature
allowable without damaging the device is 150°C. 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
JA
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
V
I
V
O
I
O
Power dissipation resulting from quiescent current is negligible.
regulator protection
The TPS764xx pass element has a built-in back diode that safely 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 is anticipated, external limiting might be
appropriate.
The TPS764xx also features internal current limiting and thermal protection. During normal operation, the
TPS764xx limits output current to approximately 800 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 165°C, thermal-protection circuitry shuts it down. Once the device has
cooled down to below 140°C, regulator operation resumes.