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From: "Gary Richardson"
Subject: Re: PLL Questions
Date: Tue, 14 Jan 2003 14:03:24 -0800
Organization: Posted via Supernews, http://www.supernews.com
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"Rene Tschaggelar" wrote in message
> Gary Richardson wrote:
> > I'm trying to design a PLL circuit and have some questions. I read the
> > section in Chapter 9 of A of E on PLLs and think I've got the general
> > However, I'm not too clear on one point, how to pick the min and max
> > frequencies of the VCO. The frequency multiplier example (pages
> > 647 - 650) generated an output signal of 61,440 Hz synchronized to 60 Hz
> > the limits on the VCO were 20 kHz to 200 kHz. Why such a wide range? Why
> > would the VCO tuning range not be centered on the target frequency, in
> > case 20 kHz to 100 kHz would seem to be more appropriate.
> > In my case I want to lock on to the 60 kHz WWVB signal.
> > What would be suitable min and max frequencies for that?
> The frequencies of a VCO are not yours to specify.
> They are given for a certain part.
> Usually an VCO operates over an octave range and not
> over a decade, this to suppress unwanted harmonics.
> If you want 61.xxkHz, any VCO which covers this frequency
> is sufficient.
> Eg 50..100kHz, 40..80kHz, and so on.
> Phase noise of of no concern yet, I guess ?
> Ing.Buero R.Tschaggelar - http://www.ibrtses.com
> & commercial newsgroups - http://www.talkto.net
Thank you for your reply. My question was not very well stated. I had
planned to use the '4060 PLL as in the examples in A of E. This device
contains a phase detector and VCO. The tuning range of the VCO is determined
by the components used (one cap and two resistors). The reply from John
Larkin answers my question in general - the tuning range of the VCO should
be just wide enough to guarantee lock. But does that hold for the '4060? Is
it impractical to try to establish a very narrow tuning range with that
device? Is that why tuning range the example in A of E is so wide?
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