[time-nuts] Digital PLL ICs, alternatives and digital loop filters
stephan at rrsg.ee.uct.ac.za
Sat Dec 16 13:52:25 EST 2006
Another question for today - I have checked out some digital PLL ICs (more
specifically the one's from AnalogDevices. It seems as if they've got some
pretty neat stuff.) As I mentioned in my previous mail: I want to lock a
GPSDOs 10MHz to a 100MHz OCXO using some sort of PLL. I find the PLL ICs
convenient because they've got everything that is needed already built-in.
Also, the phase detector and dividers are all optimised for low jitter.
Can anyone give me some pointers regarding this? If I need a low noise
100MHz output, is the digital PLL and a 100MHz OCXO a good choice? I guess
that analog PLL techniques are better, but is it worth all that effort?
Maybe I should look at PLL ICs from other manufacturers?
Also, I'm slightly worried about the thermal instabilities inherent in the
analog loop filter that is required by these PLL ICs. Has anyone
successfully chased the charge pumps output through a digital filter? Or, is
there a reason why this isn't done?
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