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Spikes caused by charge injection when plotting current at the charge pump of PLL

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QT_GIRL

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Hi guys,

i am plotting the current at the output of charge pump of PLL due to charging and discharging of Ip into the loop filter. I see some spikes and over shoots due to charge injection. I am not sure how to make a comment on the magnitude of injection. I would really appreciate if someone gives me some feedback.
thanks:cry:
 

Re: charge pump and PLL

Can you send the plots of this..... I had done some work on this some time back. I am not sure I can help you, but will try ...

BRM
 

charge pump and PLL

In my experience,only a few simulators like HSPICE allow you to view the component break up of the resulting drain current . With this you may view specifically the channel charge injection and clock feedthrough components of the current from the switches of the charge pump and make more sense of the waveforms.
I however couldn't do the same in spectre.
 

charge pump and PLL

ok thanks for your repond. do you know how to explain the charge sharing phenomenon in CP? also the channel length modulation affect of CP. I have to expalin in my project, why charging and discharging current are not the same shape and values.:(
 

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