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PLL-based CDR and PI-based CDR (Read 10637 times)
neoflash
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PLL-based CDR and PI-based CDR
Jul 26th, 2010, 9:06pm
 
Hi,

PLL-based CDR seems to be the main stream in the early days of data com. Recent ten years the PI-based design has appeared to dominate over.

What's the cons and pros of the two different architectures?

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Neo
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supermoment
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Re: PLL-based CDR and PI-based CDR
Reply #1 - Jul 27th, 2010, 12:23am
 
PI based designs have two types. One is analog PI and the other one is digital PI. digital PI is favorable and popular since it is robust and no analog filter!! the drawback is the finite resolution.
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love_analog
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Re: PLL-based CDR and PI-based CDR
Reply #2 - Jul 29th, 2010, 7:08am
 
Good question..

With PLL based ones, you need to have a PLL for each CDR.

For multi-lane I/O applications and scalability, this is expensive.

people have a central PLL, clock distribution to the I/O lanes and put a PI in each lane to generate the sampling clock.

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colossus_bade
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Re: PLL-based CDR and PI-based CDR
Reply #3 - Sep 19th, 2010, 12:00am
 
PI-based CDR will generate multi-step phase jumps when input data & local PLL have frequency offset, and will degrade jitter torlerance. If there is different SSC@input data & local PLL, this could be worse. Maybe this is the main weakpoint of PI-baseed CDR. Or there are already some cure for this problem, plz let me know, thanks very much Smiley
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love_analog
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Re: PLL-based CDR and PI-based CDR
Reply #4 - Oct 11th, 2010, 6:33am
 
Typical PI based CDR have a 2nd order loop. The integrating loop will handle the frequency difference.
So Jitter tolerance is not degraded
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SATurn
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Re: PLL-based CDR and PI-based CDR
Reply #5 - May 18th, 2011, 2:33pm
 
Hi,

Just a short addition: PLL-based CDR provides the possibility of recovering the frequency while it is limited in the PI-based CDRs.


SATurn
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BackerShu
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Re: PLL-based CDR and PI-based CDR
Reply #6 - Oct 15th, 2011, 12:29pm
 
To my certain knowledge,

PLL-based CDR usually encounters a tradeoff between the Jitter Transfer and Jitter Tolerance since their cut frequencies are dependent to each other.
Multichannel Crosstalking, as mentioned above, is also a annoying problem in PLL-based CDR.

PI-based CDR usually is limited by its phase jump, or quantization noise, and multiphase clock routing could also be a problem.


I think both of them could provide clock and data recovery.
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loose-electron
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Re: PLL-based CDR and PI-based CDR
Reply #7 - Oct 23rd, 2011, 7:47pm
 
If you already have a common clock using PI is smaller and  generally consumes less power.

if you don;t have frequency locked signal avaialble then you need the PLL.
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Jerry Twomey
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