[time-nuts] 1 PPS Correction Problem using DS1123LE-50 Delay Line

[Azelio Boriani]

Both the outputs (REF and OUT, pins 9 and 15) are affected by the jump
or only the delayed one has the problem? Anyway it is strange that a
device that can only delay a maximum of 100ns, suddenly goes into the
milliseconds. The only millisecond time I see in the datasheet is the
turn-on delay, so check that the power supply is correctly applied.

On Tue, Feb 3, 2015 at 6:20 PM, Martyn Smith <martyn at ptsyst.com> wrote:
> Hello,
>
> I am using a LEA-6T GPS chip with the DS1123LE-50 delay line to correct the
> jitter of the 1 pps output from the GPS chip.
>
> The correction works very well, dropping the peak to peak jitter of the 1pps
> output from about 20 ns to < 3 ns.
>
> However, I randomly get a big jump of the 1 pps pulse, by many
> millisceconds.
>
> After lots of research, checking code and hardware, it seems the DS1123LE-50
> chip randomly produces it's own long pulse.
>
> I have monitored the pulse going into and out of the delay line
>
> The input pulse remains constant (I can't remember exactly the pulse width,
> I think 10 us).
>
> But suddenly a large output pulse of many milliseconds appear.
>
> Some chips don't seem to have this problem.  Other chips can go wrong, 20
> times in an hour, then run perfectly for a day or so.
>
> I am blaming my software guy, he is blaming the chip.
>
> Has anyone else used this delay line and seen anything similar?
>
> This chip is now apparently obsolete, but I don't want to change yet as I
> have a few years worth of stock of these chips.
>
> Regards
>
> Martyn
>
>
>
>
>
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