TPS2044DR

The TPS2044 and TPS2054 quad power - distribution switches are intended for applications where heavy capacitive loads and short circuits are likely to be encountered. The TPS2044 and the TPS2054 incorporate in single packages four 135 - mΩ N - channel MOSFET high - side power switches for power - distribution systems that require multiple power switches. Each switch is controlled by a logic enable that is compatible with 5 - V logic and 3 - V logic. Gate drive is provided by an internal charge pump that controls the power - switch rise times and fall times to minimize current surges during switching. The charge pump, requiring no external components, allows operation from supplies as low as 2.7 V.

When the output load exceeds the current - limit threshold or a short is present, the TPS2044 and TPS2054 limit the output current to a safe level by switching into a constant - current mode, pulling the overcurrent (OCx) logic output low. When continuous heavy overloads and short circuits increase the power dissipation in the switch causing the junction temperature to rise, a thermal protection circuit shuts off the switch to prevent damage. Recovery from a thermal shutdown is automatic once the device has cooled sufficiently. Internal circuitry ensures the switch remains off until valid input voltage is present.

The TPS2044 and TPS2054 are designed to limit at 0.9 - A load. These power - distribution switches are available in 16 - pin small - outline integrated - circuit (SOIC) packages and operate over an ambient temperature range of - 40°C to 85°C.

The power switch is an N - channel MOSFET with a maximum on - state resistance of 135 mΩ (VI(INx)=5 V). Configured as a high - side switch, the power switch prevents current flow from OUTx to INx and INx to OUTx when disabled. The power switch supplies a minimum of 500 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 to less than 20 μA when a logic high is present on ENX (TPS2044) or a logic low is present on ENx (TPS2054). A logic zero input on ENx or logic high on ENx restores bias to the drive and control circuits and 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 overtemperature condition is encountered. The output will remain asserted until the overcurrent or overtemperature 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 TPS2044 and TPS2054 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 overtemperature.