SPRUJB6B November 2024 – May 2025 AM2612
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 automatic and is handled by the USB controller. 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.
Note that the USB controller is 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. In device mode, MSS_CTRL.CONTROL_USBOTGHS_CONTROL.CONTROL_USBOTGHS_CONTROL_VBUSVALID regiter bit is used to drive VBUS_VALID signal to the USB controller, as the VBUS pin is not present.