SLVSD02E March 2015 – August 2021 TPS65982
Type-C USB ports require a sink to present Rd on the CC pin before a USB Type-C source will provide a voltage on VBUS. The TPS65982 is hardware-configurable to present this Rd during a dead-battery or no-battery condition. Additional circuitry provides a mechanism to turn off this Rd when the port is acting as a source. Figure 9-10 shows the RPD_Gn pin used to configure the behavior of the C_CCn pins, and elaborates on the basic cable plug and orientation detection block shown in Figure 9-9. RPD_G1 and RPD_G2 configure C_CC1 and C_CC2 respectively. A resistance R_RPD is connected to the gate of the pulldown FET on each C_CCn pin. This resistance must be pin-strapped externally to configure the C_CCn pin to behave in one of two ways: present an Rd pulldown resistance or present a Hi-Z when the TPS65982 is unpowered. During normal operation, RD will be RD_CC; however, while dead-battery or no-battery conditions exist, the resistance is un-trimmed and will be RD_DB. When RD_DB is presented during dead-battery or no-battery, application code will switch to RD_CC.
When C_CC1 is shorted to RPD_G1 and C_CC2 is shorted to RPD_G2 in an application of the TPS65982, booting from dead-battery or no-battery conditions will be supported. In this case, the gate driver for the pulldown FET is Hi-Z at its output. When an external connection pulls up on C_CCn (the case when connected to a DFP advertising with a pullup resistance Rp or pullup current), the connection through R_RPD will pull up on the FET gate turning on the pulldown through RD_DB. In this condition, the C_CCn pin will act as a clamp VTH_DB in series with the resistance RD_DB.
When RPD_G1 and RPD_G2 are shorted to GND in an application and not electrically connected to C_C1 and C_CC2, booting from dead-battery or no-battery conditions is not possible. In this case, the TPS65982 will present a Hi-Z on the C_CC1 and C_CC2 pins and a USB Type-C source will never provide a voltage on VBUS.