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TLK2711-SP: TLK2711 maximum distance between TX and RX

ersanterinuse
Prodigy 30 points
Part Number: TLK2711-SP

Which is the maximum distance that can be taken into account for the connection between a TLK2711 TX board and a TLK2711 RX board. Making use of coaxial cables, is there any performance guaranteed up to a maximum allowable length?

  • 0
    TI__Guru 62930 points

    Alesandro,

    There is not a limit defined for the distance that can be driven.

    This is really a trade-off on many parameters that can impact the jitter budget.

    • Clock jitter (on both TX and RX GTX_CLKs)
    • clock matching (PPM difference on each end RX to TX)
    • power supply noise
    • media quality

    I am including an unpublished application note that discusses cable testing on lower cost cat5 and twinax cable.   This data was taken using SerDes devices from the same family as the TLK2711, so results should be very similar.   Using high quality coax cables should improve results shown in these test.

    I am also including a document discussing jitter and jitter budget to help.

    cabletest.pdf

    tlk2500_jitter_slla071.pdf

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade

  • 0 in reply to Wade Vonbergen
    Prodigy 30 points

    Dear Wade,

    thank you very much.

    Looking at your documents, I can understand that the media quality is important and also the length.

    Even if the cat5 cables are specified up to 200 or 350 MHz, you pushed them with data-rates up to 2.5 Gbps and it seems to work also with cable length up to 15 meters (even if with very degraded performances), correct?

    I know that the Jitter is very important and also the clock quality, but in any case, something "not-depending" by the TI boards is the cables quality and length.

    For sure making use of coaxial cables (SMA connectors) with performances up to 18 GHz, I think that the performances are better than standard low commercial cables.

    Also the transferred data-rate is important.

    Correct?

    Last question always related to TLK2711 boards: can I use them with data-rates lower than 1.6 Gbps (e.g. 1Gbps) ?

    I put "This resolved my issue" but I kindly ask you to answer to these last questions.

    Thank you very much

    Alessandro

  • 0 in reply to ersanterinuse
    TI__Guru 62930 points

    Alessandro,

    I think you could use up to 15m with utp cable.  However, it is key to manage the jitter from all sources. Primarily clocks, and media.  Performance can be degraded if poor matching (impedance or length) on board routing prior to connector.  Also noise on VDD/VDDA can cause degraded performance.

    You cannot clock the device less than 80Mhz (1.6Gbps).   That is minimum range for the PLL.

    However, you can FIFO the data, and then pack the bus with idles when waiting for more data to be sent.

    You can reference this app note on using it with a simple protocol.

    Regards,

    Wade