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, "mikecol2" <mikecol@...> wrote:
> Hi Tom,
> Thanks so much for helping with the group buy of the Si570.
Yes, thanks to Tom for doing a great job. It's so hard to get parts
like this in Australia!
Anyway, my vote is for the CMOS version. You need to convert to CMOS
at some point to make it useful for the softrock - it might as well be
on the Si570. With the CMOS output at 3.3V you can connect it directly
to the input of an HCT device at 5V and be well within spec.
Also, on the temperature stability question, don't forget that the
spec shows this for a very wide frequency range. At 50ppm over a wide
frequency range that is equivalent to an average low cost crystal.
> I had a couple of comments on the order specification.
> The new group buy web page shows the LVDS phase noise performance but
> the parts you bought are the CMOS version. Not sure which way the
> group buy is going.
> My input would be to buy the 1st Option Code: B or N code which is the
> 3.3V LVDS (High or Low OE not important to me). The spec sheet shows
> the LVDS phase noise performance which is excellent. The CMOS version
> probably isn't that great since the edge speeds are 1ns typical ( the
> LVDS and others is 350 ps max ). Also to get an indication of phase
> noise performance SI has an AN291 describing the Output Buffer
> Options. As shown in Figure 7 CMOS has the poorest jitter performance
> (translation to phase noise). The figure also shows that CML and
> LVPECL would offer the best phase noise performance. I would still
> choose LVDS because of it's ease of use, low power consumption, and
> very common standard in newer designs.
> One other consideration would be the 2nd Option Code. My choice would
> be The code B option which is 31.5ppm total stability (compared to the
> code A option which is 61.5ppm). Since we are using these for our
> radio frequency control, I think I would be worth an addition cost to
> get the higher stability. I don't know if you have priced the
> difference but it sure would be worth considering.
> As far a initial freq. I don't care that much. I like that most have
> wanted it to be for 20M (i.e. 56Mhz++). If I had to select (for my
> most used mode SSB) I would select 57Mhz. Of course there will be
> many opinions on this.
> Thanks for the consideration of LVDS output and high stability in the
> part selection.
> What do others think? Don't you want the better phase noise
> performance and stability??
> Thanks, Mike Collins KF4BQ