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DETAILED DESCRIPTION

POWER SWITCH

CHARGE PUMP

DRIVER

ENABLE (ENx, ENx)

OVERCURRENT (OCx)

CURRENT SENSE

THERMAL SENSE

UNDERVOLTAGE LOCKOUT

TPS2045A

,, TPS2046A

TPS2047A, TPS2048A, TPS2055A

TPS2056A, TPS2057A, TPS2058A

SLVS251C – SEPTEMBER 2000 – REVISED JANUARY 2008

The power switch is an N-channel MOSFET with a maximum on-state resistance of 135 m

Configured as a high-side switch, the power switch prevents current flow from OUT to IN and IN to OUT when

disabled. The power switch supplies a minimum of 250 mA per switch.

An internal charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate

of the MOSFET above the source. The charge pump operates from input voltages as low as 2.7 V and requires

very little supply current.

The driver controls the gate voltage of the power switch. To limit large current surges and reduce the associated

electromagnetic interference (EMI) produced, the driver incorporates circuitry that controls the rise times and fall

times of the output voltage. The rise and fall times are typically in the 2-ms to 4-ms range.

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 10

µA on the single and dual devices (20 µA on

turns the power 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 over temperature condition is

encountered. The output will remain asserted until the overcurrent or over temperature condition is removed.

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 TPS204xA and TPS205xA implement a dual-threshold thermal trip to allow fully independent operation of

the power distribution switches. In an overcurrent or short-circuit condition the junction temperature rises. When

the die temperature rises to approximately 140

°C, the internal thermal sense circuitry checks to determine which

power switch is in an overcurrent condition and turns off that switch, thus isolating the fault without interrupting

operation of the adjacent power switch. Hysteresis is built into the thermal sense, and after the device has cooled

approximately 20 degrees, the switch turns back on. The switch continues to cycle off and on until the fault is

removed. The (OCx) open-drain output is asserted (active low) when over temperature 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.

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Product Folder Link(s): TPS2045A TPS2046A TPS2047A TPS2048A TPS2055A TPS2056A TPS2057A TPS2058A