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TUSB4020BI: USB port identification

Amy Luo
Expert 6895 points

Part Number: TUSB4020BI

Hi team,

In TUSB4020BI circuit, 500mA LDO chip is used for 1.1V. Now the phenomenon is that USB can recognize it, but it is unstable. The port is always refreshing. What's the problem?

When the device is plugged in, the power consumption increases by 200mA. It does not supply power to the downstream port, but only reads data. Is this normal?

The circuit is as follows

Best Regards,

Amy Luo

  • 0
    TI__Guru 60870 points

    Hi Amy,

    So the hub is recognized by the host, but the hub is always refreshing?  Or are the downstream devices connected to the hub refreshing?

    Please check that SMBUSz is not pulled low, and that USB_VBUS is steady around 500 mV.  Is the clock running continously?

    Which power rail is pulling the extra 200 mA when devices are plugged in?

    Can you confirm that there is a thermal pad with adequate solder under the hub, inconsistent behavior is often linked to thermal pad issues.

    Regards,

    JMMN