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TUSB2046B: Unknown USB Device (Device Descriptor Request Failed) Message

Jim CHEN
Expert 4795 points
Part Number: TUSB2046B

Dear Team,

My customer is using TUSB2046B on their system.

The system will show "Unknown USB Devuce (Device Descriptor Request Failed)" when they use an USB cable to connect PC and upstream port of TUSB2046B.

And it also showed the yellow ban in the device manager.

CH1: USB D+

CH2: USB D-

Do we need to update driver or firmware for TUSB2046B?

Please help to advise.

Thank you.

Jim

  • 0
    TI__Guru 60870 points

    Hi Jim,

    No, there is no firmware to update in the TUSB2046B. 

    Do they have a 1.5K pullup installed on DP?  The DM line should toggle at the same time as the DP line, is it being held low?

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 4795 points

    Hi JMMN,

    Yes, they have pullup resistor on DP already. Now they have 38 pcs boards, but there are 14 pcs boards have this issue.

    Do you know how could they identify that TUSB2046 is working normally or not?

    I will ask them to try A-B-A swap to make sure the issue is relative to the chip or board.

    Thank you.

    Jim

  • 0 in reply to Jim CHEN
    TI__Expert 4795 points

    Hi JMMN,

    Today the customer find the root cause, the USB HUB will be connect normally when they asserted the HUB RESET pin,

    They tried to change the pullup resistor of RESET pin from 22 ohm to 10k ohm and then fix this symptom.

    Since the TUSB2046B reference design used 22 ohm pull up resistance for the RESET pin,

    Do you have any suggestion for the pull up resistance value?

    Thank you.

    Jim

  • 0 in reply to Jim CHEN
    TI__Guru 60870 points

    Hi Jim,

    The 22 ohm resistor pullup should only be used if the FET portion of the circuit is used.  I would recommend using a 15K pullup / .1uF capacitor circuit and check if it meets the power on reset timing shown in the datasheet.

    Regards,

    JMMN