In the case where USB power is first applied and a 20V contract established, the STUSB4500 would enable the power path to Vsnk as per usual. Then assume a 20.9V (for example) secondary power source is applied to the Vsnk output (say from a wall adapter/secondary charging port). 20.9V is within the default +5% VMONUSBH threshold, so it looks like the STUSB4500 would keep the VBUS_EN_SNK path enabled and current would flow back out of the USB port. Is this correct or is there another mechanism that would prevent this from happening?
Another way to frame the question - assume the following sequence takes place:
1) A 20V contract is established after a USB 3 PD-capable charger is attached, as per usual.
2) A 20V wall adapter is plugged in which also drives Vsnk to 20V.
3) The USB3 charger is unplugged. Will the STUSB4500 detect this removal even though Vbus will still be driven to 20V through the previously enabled MOSFETs? If not, what then happens if the USB cable is plugged into a 5V output charger?
Yet another scenario to imagine:
1) A 20V wall adapter powers an alternate power path which brings Vsnk to 20V.
2) A valid 5V capable USB charger is plugged in. Will the STUSB4500 enable the power path MOSFETs due to a valid voltage being present on VBUS_VS_DISCH, thereby shorting the wall adapter's 20V to the USB port's 5V?
