Smartphones come equipped with USB OTG functionality that allows their USB port to be used not only for charging the phone battery but also allow the smartphone to act as a USB host and deliver power to external accessories such as headphones, pen drives, and so forth. Some smartphones also support a wireless charging path which can also be used to wirelessly share power to other devices. TPS25946xx can be used as a bi-directional power switch in such applications as shown in Figure 9-2.

For the USB power path, when an external charger is connected at the port, TPS25946xx provides a conduction path from IN pin to OUT pin and the battery charger IC is configured to charge the battery and also power the internal circuits. TPS25946xx also provides overvoltage and overcurrent protection in this case. In another use case scenario where an accessory such as headphone is connected to the USB port, the phone MCU detects this and the battery charger is configured in OTG boost mode to provide power from battery to the USB port. In this case, the TPS25946xx also needs to be turned on to establish the power path from OUT to IN. Before that, there must be a minimum voltage (V_UVP(R)) available at the IN pin. An series diode and resistor is added in parallel to the device to provide this initial bias voltage. Once MCU detects that the accessory is connected, it enables the TPS25946xx and establishes a low impedance power path capable of delivering high power to the accessory.

Similarly, the TPS25946xx also provides controlled bi-directional power flow in the wireless charging and power share sub-system.