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Random jitter specification for ADCMP600 comparator

Question asked by josh.vear on May 14, 2012
Latest reply on May 27, 2012 by josh.vear

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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