NRF52840 USB VCC requirements

[lo]

Hello,

We are using NRF52840 and for a specific use case we will install our module on an M.2 (A/E) breakout. In this configuration USB will be the main communication interface and this lead to an important question : can we use the USB from the NRF52840 with only 3.3V VCC?

Bringing 5.0V to this breakout would required to add a dedicated DC boost which we really want to avoid (for various reasons) so we wonder wether there is a way to use the USB interface of the NRF52840 when providing only 3.3V VCC, even if some trick is required (for example powering the USB core with 3.3V directly from the USB_DEC pin).

The matter is rather urgent , any answer will be very welcome.

Thank you in advance.

[Sigurd]

Hi,

As mentioned by TurboJ, the VBUS USB supply voltage must be within 4.35V and 5.5V. Voltages outside this range is then  out of spec, this is not something we can recommend and correct behavior will not be guaranteed.

[lo]

OK, thank you for the confirmation, however what i wonder is wether we can power the USB core directly via DECUSB and what will append with the USBDETECT if we do so.

[Sigurd]

No, this is out-of-spec as well, and not how it's designed to be used. Worst-case you risk damaging the chip.

[lo]

ok, thank you for the confirmation.