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Any experience in design small loop filter in PLL?

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northeast1

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hung_wai_ming(at)hotmail.com said:
As in the topic
simplest is the passive filter with caps and resister
 

hung_wai_ming@hotmail.com

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forgive me that i always find someone answering not to the point.
Please see my topic. I ask "how to design a SMALL loop filter". I know the basics, OK?
 

khouly

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what do u mean by small loop filter ? , is it integrated

or what do u mean ?

khouly
 

gevy

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Charge pump current source is better.
You can decrease value of current and so to decrease value of filter capacitor and chip area.
 

hung_wai_ming@hotmail.com

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I mean on-chip loop filter and basically, we need a large capacitor on -chip. So, my question is there any good way to reduce on-chip cap?

gevy
From eqn, reducing charge pump current will reduce damping factor as well, and if you further reduce cap value, how can your PLL be stable easily?
 

terenjj

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Hi ...i an currently deisgining a loop filter(passive for a pll.

The problem is the I need a loop bandwidth of 100k to 10M.
and also my charge pump current is variable and can be varied form 1uA to 64uA
and also the n divider has 256 stages.

can some one help me out on the following ....

I would like to know how the CP and N values would affect the loop bandwidth..
how would a variable R in the Loop filter help.

thanks
 

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