View Single Post
  #5 (permalink)  
Old 05-05-2006, 10:05 AM
Rene Tschaggelar
Guest
 
Posts: n/a
Default Re: Phase alignment of DCMs on different boards/devices

Dave wrote:

>>You must distinguish between the relatively long time that th DLL takes
>>to achieve lock (many microseconds) and the very small phase error on
>>the outputs (picoseconds, which is million times shorter) once the DLL
>>is locked
>>
>>So, the different DLL will most likely achieve lock at different times,
>>but once in lock, they will each perform to data sheet specs, which
>>means picoseconds of difference on the outputs

>
>
> Hi Peter,
>
> I would have thought that if all DCMs start attempting lock at exactly
> the same time then they would achieve it at the same time. What causes
> them to achieve lock at differnt times assuming the input to each is
> exactly in phase and they start working at the same time? Is it down
> to differences between the silicon or some other inherent property of
> the DCMs loop structures?


Even if the silicon was identical to the Angstroem,
you couldn't guarantee they have the same temperature
nor that they see the same supply voltage with the
same impedance.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Reply With Quote