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Design >> Mixed-Signal Design >> charge pump mismatch, reference spur and jitter
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Message started by keikei on Mar 27^th, 2008, 8:28am

Title: charge pump mismatch, reference spur and jitter
Post by keikei on Mar 27^th, 2008, 8:28am

In a charge pump PLL, the charge pump current mismatch causes reference spur in the PLL output spectrum. Is it possible to FFT the PLL output in a transient simulation by spectre to find the reference spur? Is the mismatch or the reference spur one of the sources of PLL’s deterministic jitter?

Title: Re: charge pump mismatch, reference spur and jitte
Post by Visjnoe on Mar 28^th, 2008, 2:38am

Dear Keikei,

1. Yes, you can detect the reference spur in the PLL output by taking its FFT.

2. Yes, the reference spur is a source of deterministic jitter, since you now the exact
cause of the jitter component at this frequency (namely the reference).

Kind Regards

Peter