[time-nuts] 1 PPS 50-ohm driver

[Wojciech Owczarek]

A slightly naive question(s) perhaps, so do excuse me, but I reckon this is
a good opportunity to ask since I am approaching the same design questions
(this is a 1PPS in + 1PPS out driver for the Beaglebone Black, to/from its
PTP clock). This involves 5v / 3.3v conversion but that's another topic.

IC spec sheets are one thing, but since the Time Nuts have seen and done it
all... Why an inverting buffer? Is there an advantage in using inverted
logic for 1PPS? I have come across other timing kit that internally uses
falling edge, which is eventually inverted when interfacing with the
outside world. Is this common, and why? If my output is rising edge right
from the PWM pin I'm using to generate my 1PPS (again, separate topic), do
I gain anything by inverting it and using an inverting buffer? Is this a
matter of different rise/fall propagation delays over the various ICs?

Thanks,
Wojciech

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Wojciech Owczarek