TPS76615, TPS76618, TPS76625, TPS76627

TPS76628, TPS76630, TPS76633, TPS76650, TPS76601

ULTRA LOW QUIESCENT CURRENT 250-mA LOW-DROPOUT VOLTAGE REGULATORS

SLVS237 – AUGUST 1999

16

POST OFFICE BOX 655303

APPLICATION INFORMATION

power-good indicator

The TPS766xx features a power-good (PG) output that can be used to monitor the status of the regulator. The

internal comparator monitors the output voltage: when the output drops to between 92% and 98% of its nominal

regulated value, the PG output transistor turns on, taking the signal low. The open-drain output requires a pullup

resistor. If not used, it can be left floating. PG can be used to drive power-on reset circuitry or used as a

low-battery indicator.

regulator protection

The TPS766xx PMOS-pass transistor has a built-in back diode that 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 TPS766xx also features internal current limiting and thermal protection. During normal operation, the

TPS766xx limits output current to approximately 0.8

µA (typ). 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,

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

P

D(max) +

T

J

max

* T

A

RqJA

Where

SOIC.

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.