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AD4111 Aperture Time and Uncertainty

Hi Folks,

I would like to know what the aperture time and associated uncertainty is for the AD4111.  Can you help me understand it.  It seems to be missing from the ADC specifications.

Thank you.

  • Hi, 

    We do not specified aperture delay on any of our Sigma-Delta ADCs as any such delay between the master-clock-edge and when the ADC samples the input will be very low compared to the group-delay or settling time of the digital filter. Same with the uncertainty as the uncertainty would be largely affected by the uncertainty of the clock. We do not have jitter specification of the internal clock but the internal clock spec should effectively includes some effects of clock jitter. So if you want a better jitter then a high quality external clock or crystal is recommended. 

    May I know what is your application and why do you need such info? 

    Thanks,

    Jellenie

  • Hi Jellenie,

    Thank you for your reply.  Mostly just curious to see what the aperture time would be for this kind of ADC, and how clock jitter affects the sampling.  My guess is that the overall aperture time is equal to the number of modulator clock pulses per conversion multiplied by the modulator clock period. 

    The effects of clock jitter on the ADC output is a bit more tricky.  See the link below.

    https://www.analog.com/en/analog-dialogue/articles/sigma-delta-adc-clocking-more-than-jitter.html

    Thank you,

    Allan

  • Hi Allan, 

    I would suggest to explore this aperture time spec with other architecture such as SAR ADC for example that does not have any built in digital filter. Like I said for Sigma delta ADCs it is not relevant as it relatively low compared to the latency that the digital filter is providing to the part. One thing to note that this part is also designed for DC type of application so a poor jitter will not really a big issue. If the part could be use to digitize higher frequency AC signals then this is where a poor jitter will degrade performance.  

    Thanks,

    Jellenie