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How to solve the problem of PFD dead zone?

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Analog_IC

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Dear All,
Inserting delay into PFD is seems to be not help full.
Can somebody guide on; how to improve speed of Charge Pump to solve
dead zone problem?

Thanks
 

gajen

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Increasing delay in reset path is the way to avoid dead zone. Probably you need to check the way you are simulating PFD+Charge pump. You should look into the total charge delivered at the output of charge pump not the current output. Current output will not look very clean and it will give misleading results. Due to various caps on charge pump current would not seem like responding but the chrage delivered at output will be following the desired mismatch in ref and feedbakc clock.
 

eng_Semi

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Analog_IC said:
Dear All,
Inserting delay into PFD is seems to be not help full.
Can somebody guide on; how to improve speed of Charge Pump to solve
dead zone problem?

Thanks

It is helpfu, and most of the papers talk about it to reduce the dead zone
 

Analog_IC

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But after addition of delay there is shift in ideal graph; means at 0 phase difference
output is not zero.
And upto 100ps of phase shift output is shifted.
thanks
 

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