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Design >> Mixed-Signal Design >> RMSjitter contribution of chargepump to pll o/p. factor of 2 after integ or not?
https://designers-guide.org/forum/YaBB.pl?num=1392284490

Message started by yvkrishna on Feb 13^th, 2014, 1:41am

Title: RMSjitter contribution of chargepump to pll o/p. factor of 2 after integ or not?
Post by yvkrishna on Feb 13^th, 2014, 1:41am

Hi,

I am running pnoise simulations using spectre on chargepump.

I get a noise profile of chargepump which has flicker noise+thermal noise floor.

analytically also it should be a scaled version of current source noise with duty cycle of the square wave as shown in.. http://www.designers-guide.org/Forum/YaBB.pl?num=1389088736/1#1

since this is already 2 sided noise PSD ( which is in the form of 4kTgm ) I think we just need to integrate the noise psd (in the pll bandwidth) and multiply with PLL transfer function to output while estimating rms jitter.

However I have noticed many designers and journal papers using a factor of after integration.

Please clarify whether a factor of 2 is needed or not and why ?

Thanks,
yvkrishna