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Design >> Analog Design >> the cp current ratio between FD／CP and PD/CP in CDR.
https://designers-guide.org/forum/YaBB.pl?num=1274175670

Message started by ipmsn5 on May 18^th, 2010, 2:41am

Title: the cp current ratio between FD／CP and PD/CP in CDR.
Post by ipmsn5 on May 18^th, 2010, 2:41am

Dear all,

I start the cdr 2.5gps circuit now, would you please give me a charge pump current ratio between freq detector CP and phase detector CP?

By the way, I see some papers show that the off chip filter is better, do you think so?
:)

thanks for your help.

Title: Re: the cp current ratio between FD／CP and PD/CP in CDR.
Post by love_analog on May 31^st, 2010, 7:42am

Write the equations for the loop Bw and damping. There is no one answer. Typically you want much larger BW for the FD loop to keep acquisiton time low. For PD one, Jtol determines your BW