SLVSD02E March 2015 – August 2021 TPS65982
The TP65982 supports dead battery functionality to be able to power up from the Type-C port. This design supports dead battery using the PP_EXT path, where RPD_G1/2 and CC1/2 are connected respectively, and BUSPOWERZ is connected to GND to path 5 V VBUS into the system through the PP_EXT path. The TPS65982 will soft-start the PP_EXT (or PP_HV) path to comply with USB2.0 inrush current requirements. To enable PD functionality the TPS65982 must boot the application firmware from the flash. For the primary TPS65982, once VBUS is detected at 5 V it will automatically start to load the application firmware from the flash. The TPS65982 will then be able communicate over PD and establish a power contract at the required 20 V. Figure 10-8 shows the boot up sequence of the primary TPS65982.
When the TPS65982 that is not connected to the flash is connected in dead battery it will pass the 5 V from VBUS in to the battery charger where the battery would be able to generate the needed System 3.3 V rail to both of the TPS65982s. Once the primary TPS65982 has a valid 3.3 V supply (VBUS = 0 V on Primary TPS65982) it will load the application firmware from the flash and pass it to the secondary TPS65982 that is connected. Once the secondary TPS65982 has loaded the application firmware over UART it will be able to negotiate a 20-V power contract. Figure 10-9 shows the dead battery sequence of the secondary TPS65982.