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TUSB8041: Supplying USB_VBUS from Main 3.3V Hub Power via Divider – Is It Valid for TUSB8041?

Adam Austin
Prodigy 110 points
Part Number: TUSB8041


Tool/software:

Hi,

I’m designing a board using the TUSB8041 where the upstream port is directly connected to a Raspberry Pi CM5. In this setup, there is no physical USB connector on the upstream port, and therefore, no standard VBUS source.

The TUSB8041 is powered entirely from a 3.3V rail, which is always present during normal operation. I would like to simulate the USB_VBUS detection using a voltage divider from this same 3.3V rail, using 150 kΩ and 27 kΩ resistors, which results in approximately 0.51V at the USB_VBUS pin.

Would this configuration be acceptable?

  1. Can USB_VBUS safely be derived from the same 3.3V rail that powers the hub itself?

  2. Are there any concerns with using this divider setup in a production system?

Thanks in advance for your support.

Best regards,

  • 0
    TI__Guru*** 148730 points

    Hi Adam:

    Adam Austin said:
    Can USB_VBUS safely be derived from the same 3.3V rail that powers the hub itself?

    it's ok to connect to 3.3v, make sure USB_VBUS is around 500mv.

    Adam Austin said:
    Are there any concerns with using this divider setup in a production system?

    suggest to connect to host Vbus. If connect to 3.3v,  hub will be always active, if host  inactive, hub may get into compliance mode..

    Best

    brian