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Original question:

TUSB8020B-Q1: TUSB8020 cannot be detected through the i2c bus

TUSB8020B-Q1: Hub not able to enumerate

Yen Nee Lee
Prodigy 120 points

Part Number: TUSB8020B-Q1
Other Parts Discussed in Thread: TUSB8020B

Hi,

Currently we have issue whereby the host is not able to detect the TUSB8020B hub. We already check the connection:

- power up sequence is correct - 3.3V up before 1.1V

- USB_VBUS input 0.49V

- 24MHZ crystal input available. May i know what is the required input level? Xi is currently measured to be Vp-p 1.56V.

- SMBUSZ is NC. Measured to be 3.22V on pin.

- Reset pin is toggled after the supply is up per the spec.

May i know what other pin setting that may impact the host enumeration?

Thanks.

  • 0
    TI__Guru 60870 points

    Can you check the voltage on USB_R1?  The clock is a 1.8V input, but 1.56 Vpp should be acceptable.  Can you share a schematic?  What are the DP/DM levels on the upstream port?

    If you don't want to share a schematic on the forum, please accept my friend request and share there.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 120 points

    Hi JMMN,

    Voltage at USB_R1 is 0.511V. Is that expected voltage?

    We are not able to get any D+ D- signal at the upstream. The hub should trigger the communication upon seeing the 5V VBUS?

  • +1 in reply to Yen Nee Lee
    TI__Guru 60870 points

    The voltage on USB_R1 is ok.  When USB_VBUS goes high, DP on the upstream port should go to 3.3V and then there will be a USB reset and then a high speed handshake.  Please share a schematic.

    Regards,

    JMMN