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Original question:

DS90UB949-Q1: Stability Issue link video FPD-LINK III

DS90UB949-Q1: DS90UB949-Q1 - DS90UB948-Q1: Stability Issue link video FPD-LINK III

Angelo Morra
Prodigy 65 points
Part Number: DS90UB949-Q1
Other Parts Discussed in Thread: ALP

Hi,

 

I’m writing you because we've found an issue on FPD link III, we're using:

 

  • DS90UB949TRGCTQ1 serializer
  • DS90UB948TNKDRQ1 deserializer
  • The link is configured to work on dual-lane
  • Cable Dacar 535, HSD to HSD from Rosemberger, with characteristic impedance of 100Ohms
  • All the errata for Ser and Deser are been applied

 

Using a wiring of 36cm, a transient occurs in which the video sent to the screen flickers and sometimes even disappears, and then stabilizes and no longer manifests the phenomenon. Using cables of longer length we never find the problem.

 

A first observation of the analysis we've found a correlation between the flickers screen and lock -> unlock transition.

 

Analysis 1:

Using ALP SW we’ve run Margin Analysis Tool.

Results:


Analysis 2:

Link_Error_Count Register (Address 0x41) Deser Side has been set with 0x1F, it means maximum threshold.

Results: Flickers screen.

 

Analysis 3:

Link_Error_Count Register (Address 0x41) Deser Side has been set with 0x1F.

AEQ_TEST Register (Address 0x35) has been set initial with 0x40 and then 0x00

Results: Flickers screen.

 

Analysis 4:

Link_Error_Count Register (Address 0x41) Deser Side has been set with 0x1F.

Adaptive_EQ_Bypass Register (Address 0x44) has been set initial with 0x81, it means EQ2 = 0x0 and EQ1 = 0x4

Results: Flickers screen.

 

We would like to have your support to understand the causes, how to carry on the analysis to get the solution.

 

Thank you in advantage for your availability and support.

Angelo

 

 

 

 

 

  • 0
    TI__Mastermind 19720 points

    Hi Angelo,

    This looks to be a signal quality issue. Can you run BIST between the 949 and 948?

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Prodigy 65 points

    Hi Michael,

    we've run BIST between the 949 and 948 and on forward channel we haven't found errors. Also with Eye diagram test we have respected Eye Diagram Mask.

    Do you have other advices?

    Regards,


    Angelo

  • 0 in reply to Angelo Morra
    TI__Mastermind 19720 points

    Hi Angelo,

    When does this flickering occur? Is this flickering at startup? or at a change of the video parameters(e.x. PCLK, Resolution, refresh rate)?

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Prodigy 65 points

    Hi Michael,

    First, thank you for your support.

    At the beginning, before the analysis described above, we've found these flickering at startup and with less frequency after the start up. Using Analysis from 2 to 4, we have reduced these flickering only at start up.

    We have operated when the serializer input signal frequency is stable so when the video parameters are stable.

    Regards,

    Angelo

     

  • 0 in reply to Angelo Morra
    TI__Mastermind 19720 points

    Hi Angelo,

    Is the 949's startup following figure 32 or figure 33? Also Have you verified you are following all of the start up procedures? Also does this issue occure on many systems or just this system? 

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Prodigy 65 points

    Hi Michael,

    We've verified start up procedures and they are correct. We are following start up shown in figure 33. These flickering are on each system that we've used short cable of 36cm.

    Regards,

    Angelo

  • 0 in reply to Angelo Morra
    TI__Guru** 103215 points

    Hello Angleo,

    Especially for short cable channels, issues in the channel return loss due to impedance discontinuity in the PCB, connector, or cable design may cause issues in data reception in the high speed path. Would you be willing to share your design files so that we can help to review the layout for concerns?

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 65 points

    Hi Casey,

    Could you send me a guide to test the return loss (we're using dual lane)?
    I can't share design files in the forum, but I can share them using your email.

    Thank you,

    Regads

    Angelo 

  • 0 in reply to Angelo Morra
    TI__Mastermind 19720 points

    Hi Angelo,

    I have sent you a E2E friendship request, can you send me your design files on a private message so that I can review them privately?

    Regards,

    Michael W.