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ENABLE (ENx)

OVERCURRENT (OCx)

CURRENT SENSE

THERMAL SENSE

UNDERVOLTAGE LOCKOUT

TPS2045B, TPS2055B

TPS2046B, TPS2047B

SLVS532C – JULY 2004 – REVISED OCTOBER 2007

The logic enable disables the power switch and the bias for the charge pump, driver, and other circuitry to reduce

the supply current. The supply current is reduced to less than 1

μA or 2 μA when a logic low is present on ENx.

A logic high input on ENx restores bias to the drive and control circuits and turns the switch on. The enable input

is compatible with both TTL and CMOS logic levels.

The OCx open-drain output is asserted (active low) when an overcurrent or overtemperature condition is

encountered. The output remains asserted until the overcurrent or overtemperature condition is removed. A

10-ms deglitch circuit prevents the OCx signal from oscillation or false triggering. If an overtemperature shutdown

occurs, the OCx is asserted instantaneously.

A sense FET monitors the current supplied to the load. The sense FET measures current more efficiently than

conventional resistance methods. When an overload or short circuit is encountered, the current-sense circuitry

sends a control signal to the driver. The driver in turn reduces the gate voltage and drives the power FET into its

saturation region, which switches the output into a constant-current mode and holds the current constant while

varying the voltage on the load.

The TPS204xB/TPS2055B implements a thermal sensing to monitor the operating temperature of the power

distribution switch. In an overcurrent or short-circuit condition, the junction temperature rises. When the die

temperature rises to approximately 140

°C due to overcurrent conditions, the internal thermal sense circuitry turns

off the switch, thus preventing the device from damage. Hysteresis is built into the thermal sense, and after the

device has cooled approximately 10 degrees, the switch turns back on. The switch continues to cycle off and on

until the fault is removed. The open-drain false reporting output (OCx) is asserted (active low) when an

overtemperature shutdown or overcurrent occurs.

A voltage sense circuit monitors the input voltage. When the input voltage is below approximately 2 V, a control

signal turns off the power switch.

Copyright © 2004–2007, Texas Instruments Incorporated

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Product Folder Link(s): TPS2045B TPS2055B TPS2046B TPS2047B