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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Phase locked loops and confusion.
References: <3DDED492.2B9873B0@webaccess.net> <0lGD9.514$pN1.firstname.lastname@example.org> <3DDF7F94.25D6A972@webaccess.net>
Date: Sat, 23 Nov 2002 16:59:07 GMT
NNTP-Posting-Date: Sat, 23 Nov 2002 08:59:07 PST
Kevin Aylward wrote:
> Well I'm confused on what you mean by having a phase detector lumped
> as/with an integrator.
This came in (and I have seen it before) when people copy other
circuits. The examples the engineers copied all had the charge pump and
capacitor which is lumping an integrator into the phase detector. They
had a creature which they asked me to help the stabilize. We ended up
talking different languages because I spotted the integrator and put it
in the equation. They were convinced they had what was normal for a
phase detector and did not account for the integrator and so my
suggestions were contrary to what they read in references on the web. It
took me way too long to see that they were thinking they had a 1st order
loop while I had counted two integrators. There is nothing special here
except that this confusion has been around in two different companies I
have worked for.
Actually, I don't myself do PLLs. My job on this project is servo and
power electronics. I get pulled into the digital stuff when they think
they are looking at an analog problem living in a digital system. It is
rather interesting when a bus controller designer like one of the
engineers launches into PLLs because he and I don't always speak the
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
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