neoflash
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Mixed-Signal Designer
Posts: 397
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Hi, design1:
would you mind post the paper title of Hajimiri you mentioned here?
[quote author=design1 link=1127879810/0#0 date=1127879810]Hello,
I am trying to calculate long term jitter of my PLL by using Ken's phase domain model and then integrating the resulting noise power spectrum. However, it seems there is a factor of sqrt(2) discrepancy in the literature regarding the correct constants to apply to this integral.
In Appendix A of Hajimiri's paper, he states RMS clock jitter ^ 2 = 8 / (w0)^2 * integ(Sphi(f) * (sin (pi*f*tau))^2)
Taking the square root, letting Sphi(f)=L(f) (since the integral is from 0 to infinity) and letting tau (the measurement interval) go to infinity, the equation for RMS jitter simplifies to:
sqrt ( 4 / (w0)^2 * integ(L(f)) ) which can be re-written as 1/w0 * sqrt(4*integ(L(f)) )
However, I have found through online searches that many sources state the correct conversion to be
1/ w0 * sqrt(2*integ(L(f))) - a factor of sqrt(2) lower than Hajimiri's equation.
My time domain jitter model seems to correlate with the lower number. I'm certain I am missing something obvious, but if anyone would be kind enough to point it out I would greatly appreciate it. Thanks in advance for your response.
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