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CDCI6214EVM: Running the CDCI6214EVM off an external clock

Nicholas Barbieri
Prodigy 90 points
Part Number: CDCI6214EVM
Other Parts Discussed in Thread: TICSPRO-SW

I am trying to run the CDCI6214EVM board off of an external clock connected to the XIN port.  I initially configured the board to run off the crystal at 10 MHz.  But when a switch the reference from the crystal to LVCMOS and supply an external signal, there is no change in the board behavior and the board generated clock signal is not synchronized to the externally generate 10 MHz signal.  All the frequencies I have set are multiples of 10 MHz so synchronization should be easy, but I am having no success.

Part of the problem is I do not know the proper format for the external clock.  I am currently generating a 10 MHz square wave the varies between 0 V and 1.8 V, but the user guide provides me with very little guidance as to what I am supposed to apply. 

How do you get this board to lock to an external clock?

Thanks for the help.

  • 0
    TI__Expert 5370 points
    Hello Nicholas,

    I have assigned your question to an engineer.

    thank you for your patience.

    Regards, SImon.
  • 0 in reply to Simon Damphousse
    TI__Genius 16845 points

    Hi Nicholas,

    As I understand your post, the situation is that your output clock (board generated) is synchronized (frequency-locked AND phase-aligned) to your input clock (external clock) when you use the crystal on XIN. However, when you switch to the external reference, the output clock is no longer synchronized (frequency-locked but not phase -aligned). Is this understanding correct?

    You can phase-align the outputs with each other using the SYNC feature (see datasheet section 8.3.6). To phase-align the outputs with the input, you can configure the device in Zero Delay Mode. (see datasheet section 8.3.1.5). I hope this helps.

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    Prodigy 90 points

    Lane,

    Yes, this is exactly what I want to do.  However, I am not certain how to translate what is described in section 8.3.6 to the evaluation board and the settings within the TICSPro-SW software.  But this is a good start.

    Thanks for the help.

    Nick

  • 0 in reply to Nicholas Barbieri
    TI__Expert 5325 points
    Hello Nicholas,
    can you please let me know which components you populated on the reference paths?

    By default the REF and the XIN SMAs are connected using AC coupling caps. Both paths come with a differential termination. The XIN path has some 0 Ohms which allow to connect to the crystal on the bottom side of the PCB. You can rotate these by 90 degrees and thus connect the device pins to the transmission line leading to the SMAs.

    In your case the square wave is seen as -0.9V ... 0.9V which just misses the LVCMOS threshold.
    First order check is that R14 & R21 are populated with 0 Ohm and R15, R22 are not populated.
    As next step you can try the AC-Differential input buffer and you should be able to lock the PLL.
    To finish the LVCMOS input setup: replace C5 with 0 Ohm and remove R18.

    Is there are specific reason you want to provide the signal to XIN? You could keep the crystal in place and modify the REF path. Both paths are basically the same. So for initial cross-check you could rework REFP for your 1.8V LVCMOS square wave from your signal generator.


    Best regards,
    Patrick
  • 0 in reply to Patrick Kammermayer
    Prodigy 90 points

    Patrick,

    The reason I was using XIN is that is the only input on the evaluation board that had a connector.  I could probably install one for REF but the board doesn't come with one by default.  Would this be easier to implement?  Are you suggesting I have to remove the crystal to make use of XIN?

    Also, are you suggesting I run the board off and LVCMOS input or an AC-differential input, because those have different hardware configurations in the user's guide?  I just have the one clock signal and it appears that the ac-differential mode would require an inverted copy of the signal, which would require some electronics work on my end. 

    As far as the component populations, it is just the default configuration modified according to Table 2-1 for LVCMOS. 

    I hope that clarifies the situation.

    Thanks.

    Nick

  • 0 in reply to Nicholas Barbieri
    TI__Expert 5325 points
    Hello Nicholas,
    I'm sorry for that. This is not how it should be.
    By default the XIN, XOUT, REFP, REFN, Y1P,Y1N, Y4P & Y4N SMAs should be populated.
    Do you still have your cardboard box and your estore EVM order number? I would like to follow up on that and check what happened.

    The re-work I suggested is to match it to your signal generator setup.
    When you only want to do a quick functional check, then driving the differential stage with single ended signal through the AC capacitor will also work. I certainly recommend not to do performance tests this way, but at least you can quickly check that you have a connection from the SMA to the device pin.

    Best regards,
    Patrick
  • 0 in reply to Patrick Kammermayer
    Prodigy 90 points
    Patrick,

    This isn't even close to configuration the board was shipped to me in. For the board I have, it is populated with XIN, XOUT, Y0, Y2P, Y2N, Y3P, and Y3N. This is how it was shipped from Digikey. I can send you the purchasing details if you want to follow up on them. Probably best if I do that over email though.

    Thanks for the help.

    Nick
  • 0 in reply to Nicholas Barbieri
    TI__Expert 5325 points

    Hello Nicholas,

    the bottom left corner at the USB connector lacks some 4x DIP switch, correct?

    The EVM is likely an early product launch version. Very likely the top marking of the device has a "P" as a prefix and you can see through holes which can fit a socket.

    Please contact me using the private message system of E2E forum or the  .

    Best regards,

    Patrick