The problem of optimal zero crossing detector design was essentially
solved by Oliver Collins in the 1990's.
Essentially a series of cascaded limiter stages with appropriate gain
and bandwidth distribution are used.
With a 10MHz 1V rms signal only 2-3 stages suffices.
However unless you need fs jitter less complex zero crossing detectors
should suffice.
1) a comparator (or line receiver) based design should achieve sub 10ps
jitter.
2) AC coupling to the input of a CMOS (AC04, AHC04 LVC04) should achieve
a jitter of 1ps or less
3) A simple differential pair with AC coupled emitters (reduces
asymmetry due to component tolerances ) is capable of sub ps jitter.
There is a spreadsheet to assist design of Collins style zero crossing
detectors at:
http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html
<http://www.ko4bb.com/%7Ebruce/ZeroCrossingDetectors.html>
Bruce
paul swed wrote:
you can search time-nuts there has been a number of very good discussions
on this.
Sorry to say how you search is equally a good question.
On Thu, Jul 19, 2012 at 3:19 PM, Chris Hoffman, KG6O<cq.k...@gmail.com>wrote:
Thank you, Azelio! I don't suppose there's an impromptu FAQ page out
there, is there?
-CH
On Jul 19, 2012, at 11:58, Azelio Boriani<azelio.bori...@screen.it>
wrote:
This is sort of a FAQ: the argument was already discussed here. One of
the
most interesting idea (in my opinion) is to use an RS485 line receiver
like
the ST3485, MAX483, ADM485. They are actually transceivers so they must
be
tied permanently in RX. Since they are differential you can also put a
1:1
(or a 1:4 to raise the level) transformer to isolate the input too.
On Thu, Jul 19, 2012 at 6:03 PM, Chris Hoffman<cq.k...@gmail.com>
wrote:
Can anyone suggest a good reference design for a zero-crossing
detector? I
am trying to home an ADC sampler trigger to the 1VRMS (50ohm) 10MHz sin
from my XL-DC... And now I'm thinking that I should just home the uC
clock
to it, as well.
Essentially, I believe that I'm looking for an efficient, stable, and
accurate sine-to-square converter... and I'll welcome any advice in this
area.
This may also be used in a 1KHz 5Vpp IRIG-B decoder... I don't feel like
rectifying the signal, to be honest. I want to try to keep a smaller
BOM,
sense the waveform primarily, and crunch numbers inside the uC.
-CH
Chris Hoffman
cq.k...@gmail.com
http://ar.ctur.us
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