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Original question:

TUSB2046B NRND replacement?

TUSB2046I: TUSB2046IBVFR will show "unknow device" if DP1-4 and DM1-4 is not connected to ground. Why?

Marvin Feng
Intellectual 1340 points
Part Number: TUSB2046I

Hi Team,

Our customer is using TUSB2046IBVFR to replace TUSB2046BIVFR because TUSB2046BIVFR  is EOL . They are p2p replacement. 

They found computer will not show "unknow device" if use TUSB2046BIVFR and DP1-4 and DM1-4 are not connected to ground their 15kohm resistor. However, if use TUSB2046BIVFR, any pin of DP1-4 and DM1-4 will results in "unknow device" in PC. 

Their schematic is attached.

Thanks!

BR

Marvin

  • 0
    TI__Guru*** 141910 points

    Marvin

    We have seen this issue being reported on E2E. The DP and DM signals of the unused port need to be tied to ground with 15K resistors like the pull-downs used on the active ports. Otherwise, noise on the DP and DM could cause the USB host to think there is a USB device present.  

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Intellectual 1340 points

    Hi David,

    from our customer's feedback, it seems it is related with device description. New part's device description is different from old part. That is why it is recognized as unknown device.

    From your side, do you see this kind of difference between old part and new part?

    Thanks!

    BR

    Marvin

  • 0 in reply to Marvin Feng
    TI__Guru*** 141910 points

    Marvin

    TUSB2046I and TUSB2036BI are the same.  There were some naming quirks with the device due to how they released but they are the same part with I being the industrial temp version. Which device description are they referring to?

    Thanks

    David