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Simulators >> RF Simulators >> help on pss and pnoise analysis to PFD and CP
https://designers-guide.org/forum/YaBB.pl?num=1181194032

Message started by jeffyan on Jun 6^th, 2007, 10:27pm

Title: help on pss and pnoise analysis to PFD and CP
Post by jeffyan on Jun 6^th, 2007, 10:27pm

HI ALL,
how can i do the pss and pnoise to PFD and cp.
because when the output of cp can not get into a steady state that i can run pss.

someone told me tie a fixed voltage source to the output of cp, and run pss and pnoise, and at last, measure its noise current.

is it a right way to get the noise?

thanks,

Title: Re: help on pss and pnoise analysis to PFD and CP
Post by Ken Kundert on Jun 6^th, 2007, 10:46pm

http://www.designers-guide.org/Analysis/PLLnoise+jitter.pdf. See section 5.

Title: Re: help on pss and pnoise analysis to PFD and CP
Post by jeffyan on Jun 8^th, 2007, 12:51am

Ken Kundert wrote on Jun 6^th, 2007, 10:46pm:

http://www.designers-guide.org/Analysis/PLLnoise+jitter.pdf. See section 5.

hi ken,
the paper said:

"In this case, a representative signal would be one that produced periodic switching at the output. This
is necessary to capture the noise present during the switching process."

sorry, i don't understand very well on above, you means, i can inject two un-matched clock signals purposely, to compensate the mismatch of the charge pump currents. in this case, the output of cp can be produced periodic switching,right?
thanks.

Title: Re: help on pss and pnoise analysis to PFD and CP
Post by Ken Kundert on Jun 8^th, 2007, 11:46pm

Yes, but if the output is a current, you cannot dump it into a capacitor. The result will not reach steady-state until the output clips. Instead, dump it into a current probe as your initial post suggested.

-Ken

Title: Re: help on pss and pnoise analysis to PFD and CP
Post by jeffyan on Jun 14^th, 2007, 6:21am

hi Ken,

thanks,
you mean we can tie a constant voltage source, saying 1volts to the output of cp, and inject a clock both to the two inputs of PFD, then do pss and pnoise analysis to probe the current noise of the voltage source. is it right?

thanks again.

Title: Re: help on pss and pnoise analysis to PFD and CP
Post by Ken Kundert on Jun 14^th, 2007, 9:34am

yes