[time-nuts] Zero-Crossing Detector Design?
Chris Hoffman, KG6O
cq.kg6o at gmail.com
Thu Jul 19 20:38:57 UTC 2012
Thank you, Bruce!!! That is exactly the information I was looking for. I sincerely appreciate the help.
-CH
On Jul 19, 2012, at 12:47, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> 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.kg6o at 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.boriani at 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.kg6o at 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.kg6o at gmail.com
>>>>> http://ar.ctur.us
>>>>>
>>>>>
>>>>>
>>>>>
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