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shift clock on AD9102

I' using an AD9102 evaluation board with an AD9914 drived by a 10 Mhz clock for generating a 39.0625 Khz sinusoidal signal.

Reading this signal by an AD7760 ADC drived by the auxiliary output of the evaluation board (10 Mhz CMOS) sometime I note a shift phase between the two system. Typically the shift corresponds on 1,4 degrees in delay that is exactly one clock pulse of 10 Mhz. 

It is possible the lost of some clock pulse input?

The problem increased in case of external noise like turn on near lamps or putting a groud shield on top of the board

  • Most scopes have 8 or 10-bit resolution, but they are sampled at 100s of MHz or faster, and should have no trouble resolving 1 clock cycle at 10MHz. You only need to look at the zero-crossing, so resolution isn't important.

  • Correct !

    But I'm using a 24bits ADConverter like AD7760 because i need a phase resolution better than 1 millidegrees and only a >10Ghz scope could help me!

    I found a problem with the ground of the oscillator (TAITIEN NA-10M-2503) driving the AD9102 evaluation board. Is it possible that the sudden increase of the power supply of the thermocontrolled system generates a glitch on the 10Mhz output and only one of the two output of the AD9514 (one for AD9102 and one for AD7760) repeats the noise signal ?

  • I agree that you scope can't get the 1milli-degree resolution, but it should be sufficient for the 1.4 degree problem that you are trying to figure out. Currently you don't know if it is from AD9102 or AD7760 or AD9514 or the oscillator. If the scope doesn't show the problem, then you know it is not AD9102. If it still does, then it is unlikely to be AD7760, but could still be AD9102, or AD9514, or the oscillator.

    BTW, what do you use as a timing reference to compare you ADC's captured data to?

  • I'm using the AD9102 evaluation board output (OUT2 of AD9514) for AD7760 clock. The reading of AD7760's data (156khz) is initiated by DRDY signal of ADC.

    So AD7760 and AD9102 are sincronizated from the same clock and the phase difference should not change.

    I must trying to use the scope yet but after removing the ground problem of the oscillator the shift never occurs in normal case but only with external spikes (lamp turn-on)

  • I am glad you have resolved the issue! Just leave the lamp on Slight smile

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