SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
When either of the USB controllers assumes the role of a host, the controller is required to supply 5V to an attached device through its VBUS line. In order to achieve this task, the USB controller requires the use of external power logic (or a charge pump) capable of sourcing 5V power. The USB_DRVVBUS pin is used as a control signal to enable/disable this external power logic to either source or disable power on the VBUS line. The control on the USB_DRVVBUS is handled by the controller based on host software programming. The control should be transparent to the user so long as the proper hardware connection and software initialization are in place. The USB controller drives the USB_DRVVBUS signal high when it assumes the role of a host while the controller is in session. When assuming the role of a device, the controller drives the USB_DRVVBUS signal low disabling the external charge pump/power logic; hence, no power is driven on the VBUS line (in this case, power is expected to be provided by the external host).
Note that both USB controllers are self-powered and the device does not rely on the voltage on the VBUS line sourced by an external host for controller operation when assuming the role of a device. The voltage present on the VBUS line is used to identify the presence of a Host. The USB PHY continually monitors the voltage on the VBUS and reports the status to USB controller.