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Jee or Jcc ? in the whole PLL Jitter simulation (Read 2799 times)

tumeda

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Jee or Jcc ? in the whole PLL Jitter simulation
Sep 07^th, 2005, 6:59am

I wanna get the jitter specification of the whole PLL circuit based on these Veriloga Models of Ken's Paper.
To simplify, we assume the Jitter comes mainly from two block VCO and PFD/CP. The following questions are still not very clear for me! thanks a lot for your hints!
1. From the matlab code in list 17, the jitter can be got from "J=std(periods)".
Since the periods come from the VCO output, which are generated by the code "$abstime-prev" in List16. So I think the J is cycle-to-cycle Jitter. Is it right?
2. For the VCO block, the Jvco can be calculated by "Kvco=sqrt(c*T)". The Jvco is cycle-to-cycle Jitter, because there is no edge-to-edge jitter in VCO. So I can directly set the Jvco as the VCO period jitter value in the List 16. Is it right?
3. For the PFD/CP block, the Jee can be calculated by the formular57(Page28 ). But this Jee is edge-to-edge jitter, could I directly set the Jee as the synchronous jitter of PFD/CP in List10? or use the Jcc=sqrt(2)*Jee ???

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Ken Kundert

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Re: Jee or Jcc ? in the whole PLL Jitter simulatio
Reply #1 - Sep 7^th, 2005, 7:20am

1. J is not cycle-to-cycle jitter, it is period jitter. From your comments it seems that you might be thinking that period jitter and cycle-to-cycle jitter are the same. They are not. As can be seen in Figure 12, period jitter and cycle-to-cycle jitter are quite different.
2. J_vco is not the cycle-to-cycle jitter. It is the period jitter of the VCO when alone (when not in PLL). J_vco is the value used for the jitter parameter of Listing 16.
3. The model of Listing 10 expects the parameter jitter to be edge-to-edge jitter, so you can directly use the value computed with (57).

-Ken

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