[time-nuts] Zero-Crossing Detector Design?

Richard (Rick) Karlquist richard at karlquist.com
Thu Jul 19 22:57:26 UTC 2012


A fast comparator seems like a good idea, and it
is simple, however it is actually the last thing
you want to use.  High thermal sensitivity and high jitter.

Rick

On 7/19/2012 1:35 PM, Dan Kemppainen wrote:
> Or use a fast comparator such as an ADCMP600 series. Much lower delays,
> and faster rising/falling edges.
> FYI, I've had good luck with this at 30Mhz. You could transformer couple
> this one, or simply couple it through a cap.
>
> Dan
>
> On 7/19/2012 3:47 PM, time-nuts-request at febo.com 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.
>
>
>
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