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DS90UB960-Q1: Common mode choke selection for CSIO

Saqib Mohammad
Expert 4040 points
Part Number: DS90UB960-Q1


Hello Team,

I am working with a customer who would like to use the DS90UB960WRTDRQ1, and are considering the addition of Common-mode chokes on the CSIO port, could you kindly recommend a choke for them to consider? I did not see any on the EVM schematic or any data in the datasheet.

I saw a link/reference to an appnote on the topic but the link was broken, and did not see anything else on my E2E search related other than the one broken link.

Thanks for your help!!

Best Regards,

Saqib

  • 0
    TI__Genius 12866 points
    We will check to see if there's any CMC to recommend on CSI lanes.

    Could you also let me know in which app note you found a broken link?

    Best Regards,
    Charley Cai
  • 0
    TI__Genius 11340 points
    Hi Saqib,

    CSI signals don't need common-mode chokes. Just make sure skew matching requirements are met.

    Best,
    Jiashow
  • 0 in reply to Charley Cai
    TI__Expert 4040 points

    Hey Charley and Jiashow,

    Here is the exerpt from another E2E post which had the broken training link:

    "There is a training module on CMCs at training.ti.com/fpd-link-learning-center.

    Essentially, the CMC are there to filter out any noise created by the switching action of the gates within the device from propagating to the power sources supplying the VDD pins and causing EMI/EMC issues."

    That would be a great training to see, is it still available?

    With regards to not needing the chokes - is this something the customer could optionally use? or is it actually better to not use CMC on the CSIO lines?

    thank you!

    best,
    Saqib

  • 0 in reply to Saqib Mohammad
    TI__Genius 11340 points
    Hi Saqib,

    Yes. The training is still available. Visit the website: training.ti.com/fpd-link-learning-center and click on the topic "In-line and common mode chokes - use and effect on the transmission channel". In the training video, we talked about common mode choke being used for STP transmission for Rx ports, not for CSI ports. This is because with Rx ports, the signal has to go through a long cable which can cause skew.

    For CSI transmission, the CSI signals are typically just on the PCB and directly routed to the SoC. That's why you don't need common mode choke for this. As long as the signal skew matching requirements are met the CSI signal should be good.

    Best,
    Jiashow
  • 0 in reply to Jiashow Ho
    TI__Expert 4040 points
    Thanks! looks like the previous link included the period, so it did not work (did not notice that!). Your link worked. I will pass on this information to my customer.