We are using nRF52840 to design a M.2 module which should supports USB port. But from M.2(NGFF) spec, there is no VBUS power. There are several questions about the USB function on M.2 module:
1. Can VBUS uses +3.3V power instead? Although from the nRF52840 spec, we can see VBUS is from 4.35V to 5.5V. VBUS has two function in nRF52840 internal:
a. VBUS is used to detect USB plug in/out by VBUS,detect and VBUS,remove, and the VBUS,detect is from 3.4~4.3V, VBUS,remove is from 3.0~3.9V.
b. VBUS is used as the USB IO power input voltage, the USB IO power is a LDO and the output DECUSB is +3.3V.
So we want to know can VBUS of nRF52840 support +3.3V power? If not, PLS give us detail reason, TKS.
2. Can VBUS always keep on? We mean that VBUS is always on, then can module goes into sleep? And can USB(only D+ &D-) plug in/out be detected?
We know your current configuration can't support VBUS always on, we want to know if you change you configuration of USB function, then you can support USB sleep and plug in/out detection normal when VBUS always on.