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DS90UB948-Q1: CMC between 948 and display

Haury Zhou
Expert 6706 points
Part Number: DS90UB948-Q1

Hi team,

I find our EVMs don't have CMC in both 948 and 988 OLDI output.

But my customer is used to add CMC in the OLDI output. Generally, I know that the CMC could offset the common mode interference and improve the signal's anti-interference ability. In other words, CMC can adjust and compensate the skew between N and P channels.

What's your suggestion on the CMC? Is it a overdesign in customer's design?

BRs

Haury

  • +1
    TI__Guru** 107530 points

    Hello Haury,

    I have seen applications using CMC on oLDI traces, but the result could vary from design to design. The problem they could see is due to the fact that CMC choke acts as an AC coupling cap and will not let very low frequency components go through. I would recommend them measure the eye diagram on oLDI traces with and without the CMC and see if that affects the performance.