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DS90UB947-Q1: Cable matching length between the FPD3- Pairs

Ulrich Strobel
Prodigy 45 points
Part Number: DS90UB947-Q1

Hi Experts,
I don't see any restriction about the max. difference cable length for DOUT0 and DOUT1 Pairs in dual link mode.

Is there really no restriction?

Which mismatch is normally tolerable?

Greetings

Ulrich

  • 0
    TI__Guru 63670 points

    Hi Ulrich, 

    I will look into this, but for context is there a specific target/amount of skew/length mismatch that the customer is asking for? 

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 45 points

    Hello Logan,

    not really. I'm checking if it's possible to run both data pairs in different cables. Then I could connect two simple displays or one high-resolution display.

    I got tolerances between 1.5 and 5 cm for different lengths from the cable manufacturer. I am concerned that this will reduce the reliability of the connection.
    Hence my request.

    Regards,

    Ulrich

  • 0 in reply to Ulrich Strobel
    TI__Guru 63670 points

    Hi Ulrich, 

    Thanks for the background. 

    When doing independent mode to multiple displays/Deserializers, there is no length matching requirement at all.

    Typically for dual mode operation, a STQ cable is used where both pairs are embedded in same cable with minimal inter-pair skew/length mismatch. Up to 5cm seems surprising. 

    For dual link mode the max pair to pair skew is 1 PCLK cycle. So for example if the pixel clock is 148.5MHz, the max prop delay difference should be ~6.7ns based on the electrical prop delay through the cable. 

    Regards, 

    Logan