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Design >> Analog Design >> higher charge pump current yields lower PD noise
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Message started by casual on Aug 16^th, 2010, 1:46am

Title: higher charge pump current yields lower PD noise
Post by casual on Aug 16^th, 2010, 1:46am

"In general, a higher charge pump current yields lower phase detector noise."

What is the reason behind?
Is it because the R got to be reduced for large charge pump current in a given loop bandwidth?

Title: Re: higher charge pump current yields lower PD noise
Post by raja.cedt on Aug 16^th, 2010, 3:57am

hi,
is your question correct. I think it should be like Higher current implies lower Noise contribution from charge pump., because transfer function from charge pump to PLL out is inversely proportional to charge pump current.

Thanks,
Rajasekhar.

Title: Re: higher charge pump current yields lower PD noise
Post by casual on Aug 16^th, 2010, 4:29am

it is quoted from Prof Micheal Perrott (MIT) document...

still figuring out..

Title: Re: higher charge pump current yields lower PD noise
Post by raja.cedt on Aug 16^th, 2010, 5:30am

hi,
could you please share that doc..?

Thanks,
Rajasekhar.

Title: Re: higher charge pump current yields lower PD noise
Post by vp1953 on Aug 16^th, 2010, 11:23am

Higher charge pump current results in higher loop gain and larger loop bandwidth if the loop filter components are not changed. Larger loop bandwidth leads to greater suppression of close in phase noise.

Title: Re: higher charge pump current yields lower PD noise
Post by casual on Aug 16^th, 2010, 10:38pm

see attachment