• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 313 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TUSB4041I: USB_VBUS Connectivity

Yaron Rahamim1
Prodigy 170 points
Part Number: TUSB4041I

Hi,

In our design we intend to connect the TUSB4041I USB hub to a Raspberry Pi module.

The board is powered from a power supply.

There is no USB connector and the upstream is connected directly to the Raspberry Pi module.

How should we connect the USB_VBUS?

Currently it is connected the it to ~0.5V, which is always on, as one can see in the preliminary schematic below.

Thanks,

Yaron.

  • 0
    TI__Guru 60870 points

    Hi Yaron,

    The schematic did not post.  USB_VBUS is a detection input for the hub so it should only be high when an active host is connected to prevent interoperability issues.  Typically, we recommend avoiding the case where USB_VBUS is high before the host is out of reset.  There is considerably less chance of interoperability issues with USB 2.0 hubs than USB 3.0 hubs, but it is still preferred that USB_VBUS ramp after the host and hub are out of reset.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 170 points

    Thanks, JMMN,

    I have uploaded the picture again. As you can see, it is a simple voltage divider from the main 3.3V.

    As I understand from your answer, it might not work well, as the main 3.3V is powered before the USB hub.

    Could we connect the USB_VBUS to: A) Output port of the Raspberry Pi?; B) Power on reset device? (both via the voltage divider)

    In both options the USB_VBUS will be high after the hub and Raspberry Pi are active.

    Yaron.

  • 0 in reply to Yaron Rahamim1
    TI__Guru 60870 points

    Hi Yaron,

    If there is any signal on the board that will indicate that the host is on and ready to connect?  That is preferred.  Is the power on reset signal an active reset or a passive circuit?

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 170 points

    Hi, JMMN,

    The POR signal is an active reset.

    In any case, as you have suggested, we connected an indication signal from the Raspberry Pi.

    Thank you,

    Yaron.