Datasheet

ENABLE ( EN OR EN)
THERMAL SENSE
TPS2550
TPS2551
SLVS736B – FEBRUARY 2008 – REVISED NOVEMBER 2008 ........................................................................................................................................ www.ti.com
The logic enable controls the power switch, bias for the charge pump, driver, and other circuits to reduce the
supply current. The supply current is reduced to less than 1- µ A when a logic high is present on EN or when a
logic low is present on EN. A logic low input on EN or a logic high input on EN enables the driver, control circuits,
and power switch. The enable input is compatible with both TTL and CMOS logic levels.
The TPS2550/51 protects itself with two independent thermal sensing circuits that monitor the operating
temperature of the power-switch and disables operation if the temperature exceeds recommended operating
conditions. The device operates in constant-current mode during an overcurrent conditions, which increases the
voltage drop across power-switch. The power dissipation in the package is proportional to the voltage drop
across the power-switch, so the junction temperature rises during an overcurrent condition. The first thermal
sensor turns off the power-switch when the die temperature exceeds 135 ° C and the part is in current limit. The
second thermal sensor turns off the power-switch when the die temperature exceeds 155 ° C regardless of
whether the power-switch is in current limit. Hysteresis is built into both thermal sensors, and the switch turns on
after the device has cooled approximately 15 ° C. The switch continues to cycle off and on until the fault is
removed. The open-drain false reporting output FAULT is asserted (active low) immediately during an
overtemperature shutdown condition.
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