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CDCI6214: Output skew data when using FOD1 & IOD1 outputting a clock to Y1 & Y2 simultaneously

Part Number: CDCI6214

Hi, do you have data about the delay difference at the output pins Y1P/N & Y2P/N when these are both outputting the same clock generated by FOD1 & IOD1.

In this case ch1_mux is configured to 1h = CH1 and ch2_mux is configured to 0h = CH1.

I would like to know what the maximum phase difference between those 2 clocks will be.

Kind Regards,    

  • Output skew is given in datasheet Table 6.19. Additionally, you can use the digital delay feature to align the phase between outputs. I hope this information helps.

    Kind regards,
    Lane
  • The skew given in the datasheet are typicval values. I measured the skew between Y1 and Y2 when they are both driven by the FOD and IOD of channel 1 and I got about 500 ps of skew.

    Do you have maximum numbers for the skew spec too?

    I don't think I can use the digital delay to compensate the skew when using the same (fysicaly) FOD and IOD dividers and both outputting them on Y1 and Y2, it will just delay the clock at both outputs for the same amount of time simultaneously. right?

    Kind Regards,

    Stefaan

  • Hi Stefaan,

    I'll have a look at this and get back to you.

    Regards,

    Hao

  • Hi Stefaan,

    What you saw may be synchronization issue instead of skew. Channel divider and fractional divider add phase uncertainty. In other words, the phase relationship between output and input is not deterministic and may change after power cycle or VCO re-calibration.

    You can quickly check if the 500ps phase difference is constant every time you hit "RE-CAL" or do power cycle.

    Regards,

    Hao

  • Hi Hao Z,

    I'm not interested in the relationship between output and input. I'm interested in the relationship between two outputs (e.g. Y1 and Y2) when they are driven by only one and the same FOD + IOD dividers (by setting the ch1_mux and ch2_mux so they both select the same CH as output clock) . I thought this was what was ment by skew.

    If the ch1_mux and ch2_mux really are just a mux, the signals at the outputs of Y1 and Y2 should have only a fixed delay between them (the routing from IOD1 + delay in the ch1/2_mux etc... to the outputs Y1 and Y2). This will result in a phase difference between the clocks at the pins Y1 and Y2. I was wondering if there is information about how big this difference can be in time units.

  • Hi Stefaan,

    Sorry for the delay. I'm afraid we don't have max skew data with FOD included. However, I wasn't able to see 500ps skew between ch1 and ch2. Could you share your ticspro configuration (.tcs file. File -> Save)?

    Regards,

    Hao