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Old 10-31-2007, 07:32 PM
John Larkin
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Default Re: Ping Jim: The PFD is dead!

On Wed, 31 Oct 2007 09:38:41 -0700, [email protected] wrote:

>> I "invented" this last week. FPGAs aren't very good at implementing
>> the classic charge pump.
>>
>> http://s2.supload.com/free/PFD.jpg/view/
>>
>> The outputs here are just hard (not tri-state) logic outputs, driven
>> directly by the up/down flipflops in the pfd circuit. It's nicely
>> symmetric.
>>
>> John- Zitierten Text ausblenden -
>>
>> - Zitierten Text anzeigen -

>
>But the Inventor mentioned the additional jitter due to uncorrelated
>noise of the 2 PFD outputs and their summation in your example, and
>the evil glitches due to unmatched symmetry and parasitic coupling of
>the digital to the analog !
>This must be worth a patent.
>
>Having read
>
>http://www.keystonesemiconductor.com..._releases.html
>
>i now fear the evil glitch and deadtime jitter to corrupt my computer
>before global warming blasts icebergs and blazes glaciers.


Oh, the guy is clearly a lunatic, and an amateur lunatic to boot. His
writing is hilarious.

But the dual-diode thing solves a couple of problems using an FPGA as
a phase-frequency detector.

John

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