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TI Recommended characteristic impedance value for flex cable design

Rossinag
Expert 1705 points

Hello Nadine,

Regarding LightCrafterDisplay4710 flex cable design, 

We know the recommended characteristic impedance value for single ended signal (LS_RDATA_B, LS_WDATA, LS_CLK, LS_RDATA_A, DEN_ARSTZ) by the TI secure site flex cable document. We followed the recommended characteristic impedance value and we designed our flex cable.

But, since it is very narrow pattern width , therefore there would be a risk of cable break failure and we have difficulty about the selection of the manufacture(not so many manufactures can make such the narrow flex cable).

So, in order to make more wider pattern width flex cable , we would like to change the characteristic impedance value for single ended signal(e.g.50Ω) .Can we change the TI original characteristic impedance value for our next design?
Would you please provide TI advice?
Thank you and best regards,
Rossinag
  • 0
    TI__Genius 10495 points

    Hello Rossinag,

    In general we don't recommend the impedance change since it involves some characterization work to ensure that all signals are still meeting the specs.

    So you can change the impedance of the flex cable to 50 Ohm but you have to check if all the signals are still meeting the spec. You also have to determine the correct series termination for LS_CLK, LS_WDATA and LS_RDATA based on the measured signals. The recommended 43 Ohm is specified for 68 Ohm impedance.

    Please let me know if you have any further questions.

    Thanks,

    Nadine

  • 0 in reply to Nadine Estermann
    Expert 1705 points

    Hello Nadine,

    Thank you very much for your reply.

    We understand it.

    Best regards

    Rossinag