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DS90UB933-Q1: 933 link down

Elec Cheng
Expert 7055 points
Part Number: DS90UB933-Q1

Hi Expert,

Our customer use 933 and they have some link lost issue. Currently they find t3 is longer than 16ms. So is this the possible cause for link lost? Do we have more detailed description for this? Thanks!

BR,

Elec Cheng

  • 0
    TI__Expert 7055 points

    Hi Expert,

    Adding one question, If t3 is longer than 16ms, what kind of consequence will occur? Thanks.

    BR,

    Elec Cheng

  • 0 in reply to Elec Cheng
    TI__Guru** 103215 points

    Hello Elec,

    Yes, if the power sequence t3 < 16ms is not observed this can result in a loss of link (no FC output from the device) in some cases.

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Expert 7055 points

    Hi Casey,

    Here is some background. The issue is found in a mass production project. They can hardly change the hardware so the T3 requirement is hard to meet. Now they find there are some faulty module and are asking for solution for that. 

    Casey McCrea said:
    loss of link (no FC output from the device) in some cases.

    As you mention above, T3 > 16ms will cause link loss in some cases. The customer also would like to know if there are other causes for link loss? So they can also check and try to remedy.

    Regarding to t3 is longer than 16ms, is below programming used for remedy this? If not, do you have other solution for covering this issue? Thanks!

    BR,

    Elec Cheng

  • 0 in reply to Elec Cheng
    TI__Guru** 103215 points

    Hello Elec,

    Elec Cheng said:
    As you mention above, T3 > 16ms will cause link loss in some cases. The customer also would like to know if there are other causes for link loss?

    This is a very broad question... What I would suggest to verify is that when this issue happens; check if there is any toggling of the serializer FC output or not. If the issue is coming from this timing requirement, they would see no FC output from the SER during that power cycle. 

    Elec Cheng said:
    Regarding to t3 is longer than 16ms, is below programming used for remedy this? If not, do you have other solution for covering this issue? Thanks!

    This is the only way to address this particular timing violation and the programming needs to be done local to the 933. There is no other solution to address this timing violation 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Expert 7055 points

    Hi Casey,

    Casey McCrea said:
    check if there is any toggling of the serializer FC output or not.

    What do you mean by "FC output"? I don't see much about this in datasheet. Thanks.

    BR,

    Elec Cheng

  • 0 in reply to Elec Cheng
    TI__Guru** 103215 points

    Elec,

    FC is the FPD-Link forward channel (DOUT). If the link is down because of this power sequence issue you will see that DOUT is not toggling (you could observe the DOUT recovered signal through CMLOUT on the deserializer)

    Best Regards,

    Casey