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Pls recommend Voltage to Current converter for PLL ICO

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neoflash

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pll voltage to current

I hope the noise could be low, thanks.
 

safwatonline

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voltage current converter pll

hello.
i am really a newbie in analog design , i have a question what is ICO , about ur question why not using a charge pump , many architectures are available, if u mean gm cell u can search for (gm-c filter) u will find some gm cells "V/I converters" architectures.

regards,
a.safwat
 

neoflash

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ico pll

ICO is current controlled oscillator.

You need to first translate your Vc into current, then control the oscillator.
 

safwatonline

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hello,
i have another question, y using ICO (i thought it was called CCO) in the first place (i.e. what is the adv. over VCO, as it seems weired to me to convert current Ipump to Vc then Vc to current again )
anyway i found this and i thought it might help.
 

jcpu

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It's common to deploy GM-C structure in <100MHz oscillators,
and oscillation freqency is usually controlled by tail current.
 

safwatonline

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jcpu said:
It's common to deploy GM-C structure in <100MHz oscillators,
and oscillation freqency is usually controlled by tail current.
hello,
about GM-C what i understand is that it is a gm cell followed by a cap (filter) is this right?? , if this is right then the GM-C is used instead of the CP (plz correct me if this is wrong), then do i add another V/I after the filter (if i want to use ICO ), if so what is the diffrence between 1st and 2nd V/I cells?
sorry for the long question, but plz help as i am working in this part specially.
thnx and regards,
a.safwat
 

neoflash

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safwatonline said:
hello,
i have another question, y using ICO (i thought it was called CCO) in the first place (i.e. what is the adv. over VCO, as it seems weired to me to convert current Ipump to Vc then Vc to current again )
anyway i found this and i thought it might help.

You can not use charge pump current directly, you need a loop filter...
 

eng_islam

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hello i m a newbie in rfic design
could u tell me what is the advantages or uses of ICO
 

neoflash

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It is just the difference of definition.
 

sixth

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safwatonline said:
jcpu said:
It's common to deploy GM-C structure in <100MHz oscillators,
and oscillation freqency is usually controlled by tail current.
hello,
about GM-C what i understand is that it is a gm cell followed by a cap (filter) is this right?? , if this is right then the GM-C is used instead of the CP (plz correct me if this is wrong), then do i add another V/I after the filter (if i want to use ICO ), if so what is the diffrence between 1st and 2nd V/I cells?
sorry for the long question, but plz help as i am working in this part specially.
thnx and regards,
a.safwat
Hi, safwat

I think the first gm-c filter is function as a loop filter to replace the chargepump and loop filter in traditional PLL. The second Gm cell just to convert the voltage from the gm-c filter into current which you use to controll the oscillator.
By the way, why use a ICO? Do this kind of oscillator or PLL has better phase noise performance than traditional one?

sixth
 

safwatonline

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sixth said:
Hi, safwat

I think the first gm-c filter is function as a loop filter to replace the chargepump and loop filter in traditional PLL. The second Gm cell just to convert the voltage from the gm-c filter into current which you use to controll the oscillator.
By the way, why use a ICO? Do this kind of oscillator or PLL has better phase noise performance than traditional one?

sixth
hello sixth,
do u know what is the diffrence between using a charge pump and using gm-cell , as iwhat i understand is the both converts the up and down signals "voltage signals" to current fed into the LF , CP in a digital manner "i.e. up and down are control signals to some switches" while gm-cell is an analog block "i.e. it produces current propotional to the average of the voltage signals" , so if all that is right :D when to use CP and when to use gm cell and what is the main adv.. and disadvantages of each.
sorry 4 the long question , and thnx alot for the help
regards,
a.safwat
 

jcpu

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hello safwatonline:

We might want to look at this from control system of view:
Output of CP is proportional to the phase error,
after integration by loop filter gives this control voltage VTUNE,
which is then used for VCO or ICO.

CP output current in nowadays PLL are pulse shaped siganals,
whereas VTUNE under lock is likely to be very stable signal
with small fluctuation caused by CP injection.
They are very different mathmatically.

Hi sixth,
GmC oscillators are often used in MHz range clock generators
for reasonable current and capacitance values.
From silicon, they gives OK jitter.
But I didn't see paper discussing their phase noise in detail.
If someone find those please don't forget to inform me.
 

laglead

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hello,
I am now working on a pll consisting of V/I converter and ICO (5-inverter ring).
HOw to minized the power supply noise influence on this VCO?
Thanks!
 

jcpu

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I have similar problem too.

Some relavent discussion could be found in



not complete though, at least for me no clear picture.
 

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