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TLK2711-sp running TXCLK at 125MHz

Roberto Ramirez
Prodigy 60 points
Other Parts Discussed in Thread: TLK2711-SP, CDCM7005-SP

Hello,

I will be using the TLK2711-sp and running the TXCLK at 125MHz.  However the jitter requirement for the TLK2711 is 40ps pk to pk and I am having a hard time finding an Oscillator that will meet that jitter requirement.  Can you suggest or make any recommendations on some oscillators?

Thank You.

  • 0
    TI__Guru 62930 points

    One solution is to utilize a CDCM7005-SP and a VC(X)O to generate the clocking.  The output of the CDCM7005-SP has jitter properties very near that of the VCXO chosen.

    I am not certain what space level oscillators are out there that can have <40ps of jitter.  

    The input requirement of <40ps of pk to pk jitter is a little stringent.  It can be somewhat relaxed, as long as the frequency spectrum of the jitter is known.

    The PLL in the TLK2711 is sensitive to jitter in the range of ~300khz to 2-3Mhz.  Slower will get tracked out, faster gets attenuated by the PLL.  Jitter in this frequency range is critical, as it actually can get amplified by the PLL.

    Additionally, there are many trade-offs in a serdes link.  Some additional jitter can be tolerated, if the run is short, and higher quality media is used.  Additionally, the system may be tolerant of a higher BER rate.

    Please reference application note on jitter.  This note was created with respect to a very similar device in the same wizardlink family.

    http://www.ti.com/lit/an/slla071/slla071.pdf

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    Prodigy 60 points

    Wade,

    Thank you very much for the prompt response.  I found the application note to be very helpful.