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TUSB8020B: Crystal oscillator does not start

Petr Zkrat
Intellectual 410 points
Part Number: TUSB8020B

Hi,

Recently issues starting to appear on TUSB8020B design I inherited. The issue seems to be the same on all boards - 24MHz oscillator does not start. I verified the voltage power up and the 3ms reset mentioned in the datasheet, but everything seems to be OK. 

The crystal used is ECS-240-20-30B-TR. Changing the crystal on several boards does not help, but what always helps is to exchange the TUSB8020B chip. 

Is there anything particular what the chip is sensitive to?

Is there anything I could measure to  advance a little bit more? 

What is the crystal pins input capacitance? 

There are two vias between each crystal pin and the input pin, could this be the source of issues?

Thank you

Regards

Petr

  • 0
    TI__Guru 60870 points
    Hi Petr,

    Is this issue occurring on new boards or existing boards that were previously working? Is the upstream port connected to a USB host when you test the crystal?

    Regards,
    JMMN
  • 0 in reply to JMMN
    Intellectual 410 points

    Hi JMMN,

    the upstream port is plugged into the USB 3 port. Device manager shows Error 43- Port reset failed.

    Issue seems to happen only on new boards-when the oscillator runs on the first power-up it runs every time since then. If not, then the only thing that helps is to change the TUSB8020 chip. If I change crystal from "working board" to non-working one, the issue persists. But if the chip is swapped, it works regardless the crystal is new or old.

  • 0 in reply to JMMN
    Intellectual 410 points
    And adding to the previous- would it be possible to send few chips for investigation to TI? We have a few faulty chips that were desoldered...

    Thank you
  • 0 in reply to Petr Zkrat
    TI__Guru 60870 points

    Hi Petr,

    Do you have a local TI rep that can work with you to help submit units for retest?  Can you confirm that if you solder down a failing unit on a working board, the working board starts to fail?  The TUSB8020B will not function if there is not sufficient solder between the device and the ground pad since this is the main ground connection for the device.

    Regards,

    JMMN