TPS77001, TPS77012, TPS77015, TPS77018, TPS77025

TPS77027, TPS77028, TPS77030, TPS77033, TPS77050

ULTRA LOW-POWER 50-mA LOW-DROPOUT LINEAR REGULATORS

SLVS210C – JUNE 1999 – REVISED SEPTEMBER 1999

14

POST OFFICE BOX 655303

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,

The maximum-power-dissipation limit is determined using the following equation:

P

D(max) +

T

J

max

* T

A

RqJA

Where

SOT23.

The regulator dissipation is calculated using:

P

D +

V

I *

V

O

I

O

Power dissipation resulting from quiescent current is negligible. Excessive power dissipation will trigger the

thermal protection circuit.

regulator protection

The TPS770xx 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 TPS770xx features internal current limiting and thermal protection. During normal operation, the TPS770xx

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.