STM32MP151x: can I left the VDD3V3_USBHS Pin unconnected?

[4layer]

Hello,

according to the STM32MP151A/D Datasheet (Table 13.) the voltage on VDD3V3_USBHS Pin can be 0 ... 3.6V when USBH not used.

But on the another page of the Datasheet there is this section:

"VDD3V3_USBHS and VDD3V3_USBFS are respectively the USB high-speed and full-speed PHY supply. Voltage range is 3.07 V to 3.6 V. VDD3V3_USBFS is used to supply OTG_VBUS and ID pins. So, VDD3V3_USBFS must be supplied as well when USB high- speed OTG device is used. If not used, must be connected to VDD."

The last sentence is the opposite of the data given in Table 13.

Now I dont know what I am allowed to do? I dont need USB on my board and I dont want to add circuitry that is mandatory according to datasheets requirement: "VDDA1V8_REG must be present before VDD3V3_USBHS".

Thanks for help.

[PatrickF · Accepted solution]

Hi @4layer​ ,

I agree it is somewhat misleading, the "If not used, must be connected to VDD." will be removed from future datasheet.

If USB_VBUS/USB_ID/OTG_FS_DP/OTG_FS_DM are not used for OTG, the VDD3V3_USBFS could be either VSS (recommended), open or VDD.

If USB_DPx/USB_DMx are not used for neither USBH nor OTG, the VDD3V3_USBHS could be either VSS (recommended) or open.

These details would be provided in future AN5031 update.

Please note that not having USB OTG high-speed mean no way to flash at decent speed using CubeProgrammer (UART is extremely slow for download a complete image and JTAG is only for debugging in STM32MP platforms).

If no ethernet port available, OTG high-speed is also required to provide an Ethernet-Over-USB to allow SSH debugging (e.g. CubeIDE in production mode).

See also this similar post: https://community.st.com/s/question/0D53W00001FRAH6SAP

Regards.

[4layer]

Thank you very much for the quick and good answer.

I have Ethernet and tested Bootloader downloading with UART.