Random jitter specification for ADCMP600 comparator

I am considering using the ADCMP600 high speed comparator to detect pulses from a photo diode. The output will be fed to a time to digital converter (TDC) chip and will be part of a laser ranging system.  To maximise the timing precision of the system I need to minimise the random jitter in the comparator.  Unfortunately the data sheet for the ADCMP600 only gives values for propagation delay dispersion due to variation in overdrive and common-mode voltage.  There is no mention of random jitter.  I would like to be sure that the random jitter added by the comparator I select will be lower than the maximum allowed by the laser ranging system, however I can't find any TTL output comparators that specify their random jitter contribution.  This parameter only seems to be specified for comparators with ECL/PECL/LVDS etc differential outputs.

I suspect that the random jitter of the ADCMP600 might be good enough (I'd like it to be < 1ns rms) given that in comparators that do have a spec for random jitter it is typically much lower than both the overdrive and propagation delay dispersion (eg for ADCMP561/562 random jitter is 1ps, OD dispersion is 75ps and CMV dispersion is 10ps).  If I assume a similar relationship for the ADCMP600 which has OD dispersion 1.2ns and CMV dispersion 200ps then random jitter would be something like 20ps rms.  But is this a valid assumption?

Can anyone help?

Cheers

Josh

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  • 0
    •  Analog Employees 
    on May 23, 2012 4:15 PM

    Hi Josh-

    Sorry for the delay in response to this.  I checked with one of the apps engineers for this product and he provided the following information:

    The 600 series offers three different speeds. The ADCMP600/1/2/3 are the slowest with 3ns propagation delay and approximately 4ns output rise times.  The ADCMP604/5 are faster with 1.6ns propagation delay and approximately 600ps output rise times.  Finally the ADCMP606/7 have 1.2ns propagation delay, approximately 160ps output rise times and typically 2ps rms jitter. For comparison we setup and measured a ADCMP604 on the bench at 10ps rms jitter, 70ps Pk-Pk jitter. Both the ADCMP604/5 or ADCMP606/7 are candidates for the application mentioned.

     

    I hope this helps.

     

    Regards,

    AndyR

    EngineerZone Community Manager


Reply
  • 0
    •  Analog Employees 
    on May 23, 2012 4:15 PM

    Hi Josh-

    Sorry for the delay in response to this.  I checked with one of the apps engineers for this product and he provided the following information:

    The 600 series offers three different speeds. The ADCMP600/1/2/3 are the slowest with 3ns propagation delay and approximately 4ns output rise times.  The ADCMP604/5 are faster with 1.6ns propagation delay and approximately 600ps output rise times.  Finally the ADCMP606/7 have 1.2ns propagation delay, approximately 160ps output rise times and typically 2ps rms jitter. For comparison we setup and measured a ADCMP604 on the bench at 10ps rms jitter, 70ps Pk-Pk jitter. Both the ADCMP604/5 or ADCMP606/7 are candidates for the application mentioned.

     

    I hope this helps.

     

    Regards,

    AndyR

    EngineerZone Community Manager


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