Hi,
I want to have a nrf52840 communicating with a Raspberry Pi over USB. The single USB port of Raspberry Pi 3A+ is also used by a LTE modem. So I have an USB hub IC to handle both.
The board has +5V and +3.3V available. I want to use a USB cable with only the data (D+/D-) lines.
Is it possible to power the nrf52840 like this :
- VDD shorted with VDDH with 3.3V
- VBUS pin supplied with direct 5V
The VBUS voltage would not come from the VBUS line of the USB cable as there's none in the cable used.
It would be like "Circuit configuration no. 3 schematic" for nrf52840-QIAA.
Feeding directly 5V to the VBUS pin of nrf52840 would avoid buying a chip like a TPS2042 just for it because I already feed the LTE modem directly in another board and not via the VBUS line of the cable.