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.