[time-nuts] Isolated 1PPS-input for distribution-amp?

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Aug 31 09:07:09 EDT 2017


HCPL7101 and similar 50MBaud optocouplers claim 50ps rms jitter.

Some non optical isolated couplers specify ~30ps jitter.


Bruce

> 
>     On 01 September 2017 at 00:12 Anders Wallin <anders.e.e.wallin at gmail.com> wrote:
> 
>     Hi all,
>     I'm looking for a solution for galvanic isolation of a 1PPS signal-input to
>     a distribution amplifier.
> 
>     We have an old box using HCPL-2411 at the input followed by 74LS04, but the
>     degraded rise-time (from below 3ns out of a clock, to >12 ns out of the
>     box) and increased jitter (from below TIC-resolution of 20ps out of the
>     clock to 700ps std.dev at 100s out of the box) are now limiting our
>     measurements.
> 
>     Does anyone have experience with a circuit with good rise-time and low
>     jitter?
>     Should I look for better optoisolators, or pulse-transformers, or something
>     else?
> 
>     thanks for your input!
>     Anders
> 
>     PS. I started on publishing my distribution-amplifier (non isolated) on the
>     ohwr.org site, see https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/wiki
> 
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