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Simulators >> RF Simulators >> PFD simulation problem with EldoRF
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Message started by trashbox on Aug 31^st, 2005, 2:26am

Title: PFD simulation problem with EldoRF
Post by trashbox on Aug 31^st, 2005, 2:26am

Hi all,
I used EldoRF to simulate the phase noise of PFD in PLL. However, the steady-state analysis can not be converged so that EldoRF can not continue the phase noise analysis. I have changed the related options(reltol & eps, sst_convergence_help etc.), there is no use.

Then I put some small capacitors(~2fF) on the nodes of PFD's circuit by hand. For example, on the nodes of INV's output and DRAIN of nmos in NAND. The steady-state analysis of PFD can be converged. Why?

If my circuit is very complicated(i.e.,I can not put small capacitors by hand in the netlist file) and I also can not find any commands which can add small capacitors on the node automatically. How to solve the steady-state analysis convergence problem during PFD simulation?

Thank you very much.

Title: Re: PFD simulation problem with EldoRF
Post by dguser on Sep 13^th, 2005, 1:39pm

Hi,

I am curious what is the number of harmonics that you used in the simuation. Also did you turn on the pre-conditioner (option SST_PRECONDITION) and increase the solver iteration limit (option SST_MAX_LINITER)?

I would try TIME for pre-conditioner and increase the number of harmonics. If still fails, I would contact the Mentor folk.

P.S: I am new to this forum. I tried to reply to this post earlier but am not sure if it went through. Anyway, sorry if you get duplicate responses.