[time-nuts] Re: PICDIV stability (was: Crystal oscillator for a begginer)

[Magnus Danielson]

Hi,

The traditional way is to lock an oscillator and look at the phase 
detector output.

You get a high-pass filter from the locking, but for many purposes 
that's just fine.

In some cases it is called "the golden PLL method".

Cheers,
Magnus

On 2022-01-09 18:04, Marek Doršic wrote:
> Is there any method to measure random jitter without TimePod or scopes costing a small fortune?
>
>      .md
>
>> On 9 Jan 2022, at 01:21, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
>>
>> Yes, that post is full of misleading information.
>> The TI document is irrelevant as the PIC based divider doesn't have non harmonically related signals using the same chip.
>> All internal signals within the PIC are harmonics of the divided output signal.
>> The post did not distinguish between random jitter and data dependent jitter etc. Either the poster doesn't understand the finer details of frequency division or the post is intended to mislead.
>>
>> Bruce
>>> On 09/01/2022 12:55 Angus via time-nuts <time-nuts at lists.febo.com> wrote:
>>>
>>>
>>> Maybe it got mashed up, but I only linked to one post, and that
>>> addressed the specific question that had been asked. There is also, as
>>> far as I know, no 'misinformation' in it. However if anything does
>>> need corrected, I can easily do that.
>>>
>>>   One of the main reasons that I did the test was all the actual
>>> (IMHO...) misinformation that was in the thread about the PIC
>>> dividers. I find them very useful and have not had any problems with
>>> them, but since they are mostly used on 53131As which do not have a
>>> very high resolution, I also wanted to see if I was missing anything.
>>>
>>> As far as I can see, it showed just what is going on as well as I
>>> could have expected with that scope, os I don't quite agree that
>>> *everything* should be ignored :)
>>>
>>> Angus.
>>>
>>>
>>> On Sat, 8 Jan 2022 14:00:28 +1300 (NZDT), you wrote:
>>>
>>>> That entire thread is full of misinformation and should be ignored unless one understands the difference between random and data dependent jitter.
>>>>
>>>> For a well designed divider with a single output frequency only the random jitter spec is significant.
>>>>
>>>> One doesn't need a bunch of expensive LeCroy gear to measure RJ of such dividers as its PN manifestations are readily apparent and measurable.
>>>>
>>>> Using one of the supposedly super low jitter flipflops isn't a panacea. In practice unless an appropriately designed ZCD is used the wideband input noise of the very fast FF will dominate and produce much more jitter than expected due to the relatively slow slew rate of the outputs of most 10MHz sources.
>>>>
>>>> Bruce
>>>>
>>>>> On 08/01/2022 12:40 Angus via time-nuts <time-nuts at lists.febo.com> wrote:
>>>>>
>>>>>
>>>>> On Fri, 07 Jan 2022 12:40:49 -0800, you wrote:
>>>>>
>>>>>>> The two biggest outside influences on the PICDIV are supply voltage and temperature.
>>>>>> Another interesting influence is the number of outputs that are switching and
>>>>>> the load on them.  In particular, if you have several outputs running at
>>>>>> different frequencies, the clock-out delay should be slightly longer when 2
>>>>>> outputs switch when compared to when only one is switching.
>>>>>>
>>>>>> Has anybody measured that on a PIC? (or similar chip)
>>>>>>
>>>>>> I think one of tvb's picDEVs has several outputs.
>>>>> To some extent:
>>>>> https://www.eevblog.com/forum/projects/easiest-way-to-divide-10mhz-to-1mhz/msg3257018/#msg3257018
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