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SN75DP122A EMI problem

Harson
Expert 3700 points

Hi,  all

My customer BYD using this part for DP port, while in EMI test, at 1.6GHz, the performance can't meet the requirement, about 2db higher.

Here is the spec about the Common Mode choke, and their sch.

I have a question abou the DLW21SN900SQ2, it's a 90Ohm @100MHz. If i suggest change to 120Ohm, does it help for lower EMI?

or how can get a lower EMI?

Thanks.

here is the sch,

  • 0
    TI__Expert 6745 points

    You do realize you posted a proprietary schematic on an open site...  Please refrain from doing this in the future.

     

    For EMI solutions, it is almost always involving layout and possibly schematic additions, such as the common mode choke.  I also notice that there is a Parade redrive (PS8121EDQFN48G) after the DP122.  The DP122 is basically a voltage follower and just replicates the input, while the DP redriver will create a signal that has full amplitude and emphasis settings of the channel.  As such, this question really should be asked of the Parade application group.  If the DP120 was used, then I would not only recommend the common mode choke you have selected, but I would also want to look at the layout associated with the ESD structures (RCLAMP0524P) for possible impedance discontinuities the will cause EMI.

  • 0 in reply to Ken Shaw
    TI__Expert 3700 points

    Hi, Ken

    Thank you very much!

    Customer wonder if there are any setting in DP122A that can slow the edge or similar technologies which can improve the EMI performance.

    i have read the datasheet, there is no such function, but i would like to double conferm with you.

  • 0 in reply to Harson
    TI__Expert 6745 points

    There are no setting options for edge rate control for the DP122A