Why do we do a quadratic add of jitter when calculating total jitter. For example, with an input jitter of +/- 100 pS, and a DCM jitter of
Because the jitter has a statistical distribution.
If your jitter were 100 ps deviation where the deviation is sinusoidal at 10 kHz added to a 9 kHz sinusoidal jitter deviation (these are not realistic situations) the jitter will add.
If you use 6 sigma values for peak-to-peak, the values will add to give you a 12 sigma probability which is way beyond the 6 sigma value you're using for the peak-to-peak result.
RMS noise is a quadratic add for amplitude measurements.
RMS jitter (or the scaled peak-to-peak jitter) is also a quadratic add.
- John_H
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