LP2951 datasheet(21/47 Pages) TI

21 / 47 page

6.3.4 Undervoltage Lockout (UVLO)

The device has an independent undervoltage lockout (UVLO) circuit that monitors the input voltage, allowing a

controlled and consistent turn on and off of the output voltage. To prevent the device from turning off if the input

drops during turn on, the UVLO has hysteresis as specified in the Electrical Characteristics table.

6.3.5 Thermal Shutdown

The device contains a thermal shutdown protection circuit to disable the device when the junction temperature

(TJ) of the pass transistor rises to TSD(shutdown) (typical). Thermal shutdown hysteresis verifies that the device

resets (turns on) when the temperature falls to TSD(reset) (typical).

The thermal time-constant of the semiconductor die is fairly short, thus the device cycles on and off when

thermal shutdown is reached until power dissipation is reduced. Power dissipation during start up is potentially

high from large VIN – VOUT voltage drops across the device or from high inrush currents charging large

output capacitors. Under some conditions, the thermal shutdown protection disables the device before start-up

completes.

For reliable operation, limit the junction temperature to the maximum listed in the Recommended Operating

Conditions table. Operation above this maximum temperature causes the device to exceed operational

specifications. Although the internal protection circuitry of the device is designed to protect against thermal

overall conditions, this circuitry is not intended to replace proper heat sinking. Continuously running the device

into thermal shutdown or above the maximum recommended junction temperature reduces long-term reliability.

6.4 Device Functional Modes

6.4.1 Shutdown Mode

This device can be placed in shutdown mode with a logic high at the SHUTDOWN pin. Return the logic level low

to restore operation or tie SHUTDOWN to ground if the feature is not being used.

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LP2951-Q1

SLVSAW6H – JUNE 2011 – REVISED NOVEMBER 2024

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LP2951 Datasheet(PDF) 21 Page - Texas Instruments