An important feature of USB Type-C and USB PD is the ability for this connector to serve as the sole power source to mobile devices. With support up to 100 W, the USB Type-C connector supporting USB PD can be used to power a whole new range of mobile devices not previously possible with legacy USB connectors.

When the USB Type-C connector is the sole power supply for a battery powered device, the device must be able to charge from the USB Type-C connector even when its battery is dead. In order for a USB Type-C power adapter to supply power on V_BUS, RD pulldown resistors must be exposed on the CC pins. These RD resistors are typically included inside a USB Type-C CC/PD controller. However, when the TPD4S311 is used to protect the USB Type-C port, the OVP FETs inside the device isolate these RD resistors in the CC/PD controller when the mobile device has no power. This is because when the TPD4S311 has no power, the OVP FETs are turned off to guarantee overvoltage protection in a dead battery condition. Therefore, the TPD4S311 integrates high-voltage, dead battery RD pull-down resistors to allow dead battery charging simultaneously with high-voltage OVP protection.

If dead battery support is required, short the RPD_G1 pin to the C_CC1 pin, and short the RPD_G2 pin to the C_CC2 pin. This connects the dead battery resistors to the connector CC pins. When the TPD4S311 is unpowered, and the RP pull-up resistor is connected from a power adaptor, this RP pull-up resistor activates the RD resistor inside the TPD4S311. This enables V_BUS to be applied from the power adaptor even in a dead battery condition. Once power is restored back to the system and back to the TPD4S311 on its VPWR pin, the TPD4S311 turns ON its OVP FETs in 3.5 ms and then turns OFF its dead battery RD. The TPD4S311 first turns ON its CC OVP FETs fully, and then removes its dead battery RDs. This is to make sure the PD controller RD is fully exposed before removing the RD of the TPD4S311. This is to help ensure the USB Type-C source remains attached because a USB Type-C sink must have an RD present on CC at all times to guarantee according to the USB Type-C spec that the USB Type-C source remains attached.

If desiring to power the CC/PD controller during dead battery mode and if the CC/PD Controller is configured as a DRP, it is critical that the TPD4S311 be powered before or at the same time that the CC/PD controller is powered. It is also critical that when unpowered, the CC/PD controller also expose its dead battery resistors. When the TPD4S311 gets powered, it exposes the CC pins of the CC/PD controller within 3.5 ms, and then removes its own RD dead battery resistors. Once the TPD4S311 turns on, the RD pull-down resistors of the CC/PD controller must be present immediately, in order to guarantee the power adaptor connected to power the dead battery device keeps its V_BUS turned on. If the power adaptor does not see RD present, it can disconnect V_BUS. This removes power from the device with its battery still not sufficiently charged, which consequently removes power from the CC/PD controller and the TPD4S311. Then the RD resistors of the TPD4S311 are exposed again, and connects the power adaptor's V_BUS to start the cycle over. This creates an infinite loop, never or very slowly charging the mobile device.

If the CC/PD Controller is configured for DRP and has started its DRP toggle before the TPD4S311 turns on, this DRP toggle is unable to guarantee that the power adaptor does not disconnect from the port. Therefore, it is recommended if the CC/PD controller is configured for DRP, that its dead battery resistors be exposed as well, and that they remain exposed until the TPD4S311 turns on. This is typically accomplished by powering the TPD4S311 at the same time as the CC/PD controller when powering the CC/PD controller in dead battery operation. When protecting the TPS6598x family of PD controllers with TPD4S311, this is accomplished by powering TPD4S311 from TPS6598x's LDO_3V3 pin (connect TPS6598x's LDO_3V3 pin to TPD4S311's V_PWR pin).

If dead battery charging is not required in your application, connect the RPD_G1 and RPD_G2 pins to ground.