What are the advantages of Analog PLL over Digital PLL

advantages of pll

Hi all

could you answer my question please

thanks

analog pll

The only advantage is low jitter.

advantages digital pll

elec-eng said:

Hi all
could you answer my question please
thanks

Click to expand...

Perhaps it makes sense first to clarify what you really mean as the phrase "digital PLL" is used in several ways. Some people mean only a digital PD/PFD and some other really mean "complete digital" (including filter and a number controlled oscillator)

digital pll advantages

Within the context of actual developments

for instance the TI driven time versus voltage driven argument

http://www2.iccad.com/data2/iccad/iccad_05acceptedpapers.nsf/9cfb1ebaaf59043587256a6a00031f78/e25be1f58da7d131872570530070afb2/$FILE/2A_3slides.PDF

by this guy

http://www.faqs.org/patents/inv/236491

it is a path to preserve system performance in the presence of NONscaling

Analog does not profit in general from further scaling but price and SOC aspects contrain analog to search for alternatives.

Digital PLL is one!

But VCO is analog, beside digital driven. The missing part is the high resolution phase detector. Analog phase detectors could easy resolve 200fs-1ps of a 20ns reference clock. The effort to built an 200fs resolving, 20ns range TDC is higher than everything else.

So a litle digital here and there to avoid NONscaling analog issues!

Re: digital pll advantages

rfsystem said:

Analog phase detectors could easy resolve 200fs-1ps of a 20ns reference clock.

Click to expand...

I was looking for a paper that proves these numbers. Unfortunately, it's easy to find PFD resolutions for TDCs but not for analog PDFs. Anyone can suggest me a paper? Thanks