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LMH1229: LMH1229: Recovered has more high frequency jitter than expected

Gwyn Doherty
Prodigy 30 points

Part Number: LMH1229

I am using the LMH1229 equalizer for the very first time. Its replaces an older part. I am particulary impressed with its longer cable length support at 12G. However, I am measuring more high frequency jitter than I would expect on the OUT1 for all data rates. This has been configured to drive out the recovered clock 297Mhz for 12G/6G. 

Great care has been taken to follow the PCB layout recommendations but is there anything that might compromise the jitter? This is causing us issues and we might have to go back to the old part if we can't resolve this.

  • 0
    TI__Mastermind 37185 points

    Hi Gwyn,

    Does OUT1 show worse jitter than OUT0? These outputs ought to have similar jitter seeing as they both pass through the CDR:

    If OUT0 does have better jitter, do you notice any difference in the layout between OUT1 and OUT0?

    How much jitter are you seeing at OUT1 with 12G signaling? I'd like to see how it compares to our datasheet plots for jitter:

    Last question: Is this question related to this other E2E thread? If so, I'd like to consolidate these into one thread so we have all the details in one spot. Perhaps we can continue on the linked thread.

    Best,

    Shane