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TUSB8044A: VBUS control

Takahiro Saito
Expert 5455 points
Part Number: TUSB8044A

Hello team,

How does this device detect the downstream device? Is VBUS needed in the downstream side?

As an input to USB_VBUS, is it able to control by using power that is not from connected USB device?

For example, if 0.5V is applied without using voltage divider, does the device work correctly?

Regards,

Saito 

  • 0
    TI__Guru 60870 points

    Hello Saito-san,

    Downstream port VBUS control is not needed.  If the hub PWRCTLx outputs are not used to control downstream power, set the FULLPWRMGMTz input high so that it is reported in the USB descriptors of the hub that it doesn't have full power control of the ports.

    USB_VBUS can be supplied by any source as long as it does not exceed the maximum voltage rating.  Also, USB_VBUS should not be pulled high unless there is an active powered upstream connection, if USB_VBUS is pulled high and there is nothing connected to the upstream port of the hub, the hub will enter a low power state and when a host is later connected, the host and the hub could get out of sync (one being active, the other in low power state).

    Regards,

    JMMN