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TUSB4020BI: About USB_VBUS

diverger
Expert 1275 points
Part Number: TUSB4020BI

Hi,

My design is a self-powered USB2.0 hub. I want to know the detailed role of USB_VBUS as the datasheet only states the pin must be connect to VBUS through a voltage divider with given resistor values. There must be some voltage thresholds for this pin, right? What will the chip do when the USB_VBUS over/under these threshold? I need to know the thresholds in order to connect this pin to another voltage rather than VBUS to do something like power on/off sequencing.

Thanks.

  • +1
    TI__Guru 60870 points

    Hi,

    The function of upstream VBUS in a hub is defined by the USB 2.0 specification (see 7.1.7.3).  I would recommend adjusting the resistor values so that the USB_VBUS is around 500mV when VBUS is on.  The USB_VBUS will start to detect VBUS on at 400 mV.

    Regards,

    JMMN