Which is the primary supply for VDDD in CCG3 - VBUS or VSYS?
According to the current configuration of CCG3 firmware, the VSYS power switch is always ON. The VSYS supply takes higher priority when both VBUS and VSYS are present, because the VSYS switch is always ON. When VSYS goes below the minimum specified voltage of 2.7 V (for example, in a dead battery condition), then the LDO is turned on and the VDDD is supplied by VBUS. The LDO converts the VBUS input to 3.3 V.