[time-nuts] DDS module

[Tim Shoppa]

SG8002 is definitely a distributor programmable unit.

It is a digital synthesizer in a can with no effort towards clean output.

PLL? They would not bother to put a cleanup PLL in the can for the
intended microprocessor application.

Tim N3QE

On 7/21/13, Didier Juges <shalimr9 at gmail.com> wrote:
> I am familiar with the Epson Seiko SG8002 series and nowhere does it say
> they are programmable. They are not user programmable for sure, only the
> distributor has the tools to do it. The data sheet does not have any
> information that would be a hint that they are PLL's.
>
> Http://WWW.KO4BB.com/Timing/MicroprocessorCrystals.php
>
> Didier
>
> Hal Murray <hmurray at megapathdsl.net> wrote:
>>
>>lists at rtty.us said:
>>> A number of them are sigma delta PLL's and have some really nasty
>>jitter and
>>> spur issues. Anything that shows up listed as "user programmable" -
>>watch
>>> out.
>>
>>But "user programmable" won't find all the nasty ones.
>>
>>I haven't been looking recently.  There used to be some that were field
>>
>>programable.  The idea was that the distributor would do it so you
>>didn't
>>have to wait for the factory to grind the crystal to order if you
>>wanted an
>>oddball frequency.  They didn't mention the PLL in the data sheet.  You
>>had
>>to read between the lines.
>>
>>I assume the distributor stocked a handful of basic frequencies and
>>there was
>>a PC that told them which one to use and did the programming if you
>>told it
>>what frequency you wanted.
>>
>>It looks like a fun math problem.  How many frequencies do you need to
>>stock
>>in order to cover a given frequency range with a given PLL chip?  The
>>result
>>doesn't have to be a direct hit.  You can include some fudge as part of
>>the
>>overall accuracy spec.  (If you claim 100 PPM, but cut the crystal
>>within 50
>>PPM, then you have 50 PPM left for the PLL.)
>>
>>
>>
>>--
>>These are my opinions.  I hate spam.
>>
>>
>>
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