TPS54380PWPR datasheet(13/21 Pages) TI

13 / 21 page

TPS54380

SLVS454B − JANUARY 2003 − REVISED FEBRUARY 2005

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OVERCURRENT PROTECTION

The cycle-by-cycle current limiting is achieved by sensing

the current flowing through the high-side MOSFET and

comparing this signal to a preset overcurrent threshold.

The high-side MOSFET is turned off within 200 ns of

reaching the current limit threshold. A 100-ns leading edge

blanking circuit prevents the current limit from false

tripping. Current limit detection occurs only when current

flows from VIN to PH when sourcing current to the output

filter. Load protection during current sink operation is

provided by thermal shutdown.

THERMAL SHUTDOWN

The device uses the thermal shutdown to turn off the power

MOSFETs and disable the controller if the junction

temperature exceeds 150°C. The device is released from

shutdown automatically when the junction temperature

decreases to 10°C below the thermal shutdown trip-point,

and starts up under control of the slow-start circuit.

Thermal shutdown provides protection when an overload

condition is sustained for several milliseconds. With a

persistent fault condition, the device cycles continuously;

starting up by control of the soft-start circuit, heating up due

to the fault condition, and then shutting down on reaching

the thermal shutdown trip-point. This sequence repeats

until the fault condition is removed.

POWERGOOD (PWRGD)

The power-good circuit monitors for under-voltage

conditions on VSENSE. If the voltage on VSENSE is 10%

below the reference voltage, the open-drain PWRGD

output is pulled low. PWRGD is also pulled low if VIN is

less than the UVLO threshold or ENA is low, or a thermal

shutdown occurs. When VIN ≥ UVLO threshold, ENA ≥

enable threshold, and VSENSE > 90% of Vref, the

open-drain output of the PWRGD pin is high. A hysteresis

voltage equal to 3% of Vref and a 35-µs falling edge

deglitch circuit prevent tripping of the power-good

comparator due to high-frequency noise.

TPS54380PWPR Datasheet(PDF) 13 Page - Texas Instruments