The TPS20xxB are current-limited, power-distribution switches providing 0.5-A continuous load current. These devices incorporates 70-mΩ N-channel MOSFET power switches for power-distribution systems that require multiple power switches in a single package. Gate driver is provided by an internal charge pump designed to minimize current surges during switching. The charge pump requires no external components and allows operation supplies as low as 2.7 V.
The power switch is an N-channel MOSFET with a low on-state resistance. 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 current of 500 mA.
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 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 logic enable pin 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 high is present on EN. A logic zero input on EN 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 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 TPS20xxB 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.
There are no other functional modes for TPS20xxB devices.