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CHG PUMP UP/DN current mismatch in synthesizer (Read 1637 times)

neoflash

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Mixed-Signal
Designer

Posts: 397

CHG PUMP UP/DN current mismatch in synthesizer
May 17^th, 2011, 10:45pm

Frequency synthesizer suffers from higher spur level when CHGPMP up down current is not exactly the same. The mismatch distorts the transfer function of the PFD/CP and cause non-linearity.

I have ever heard that some people utilized a special type of PFD to solve this problem. Can people point me to the reference or describe the idea briefly?

Thanks,
Neo

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: CHG PUMP UP/DN current mismatch in synthesizer Reply #1 - May 18^th, 2011, 5:54pm if it is just a current mismatch, then the problem is no big deal - you get a higher current for pump up or down, changing the BW response characteristic a little. When you are talking spectral spurs, thats a different issue.
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