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Re: [softrock40] Si580 Group buy Output levels, Temp Stability Options

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  • T Hoflich
    ... Mike, Thanks for your excellent comments. My goal in doing this was to add to the softrock experience at minimum cost and simple implementation with
    Message 1 of 60 , Nov 1, 2007
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      --- mikecol2 <mikecol@...> wrote:

      > Hi Tom,
      >
      > Thanks so much for helping with the group buy of the
      > Si570.
      >
      > 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

      Mike,
      Thanks for your excellent comments.
      My goal in doing this was to add to the softrock
      experience at minimum cost and simple implementation
      with reasonable performance.
      I read AN291 in my research and chose CMOS because it
      seemed the easiest to use and is typically used below
      160 MHz. Besides, I don't know how to interface LVDS
      to the softrock. Also, CMOS draws less power which is
      not a big issue. The noise performance of the CMOS
      version is much better than any other chip that I am
      aware of by quite a bit.
      I am certainly not against the lowest possible noise
      and best stability.
      A couple of questions to consider. Will anyone notice
      the slightly less noise? I know from my experience
      that the stability is not a problem as I can copy
      PSK31 all day long.
      Since the demand is so high, maybe I could offer a
      cheap version and a more expensive version for those
      who want or need it.

      But, I will try to do whatever the group wants.
      So, sound off.

      73, Tom KM5H
    • Leon
      ... From: k5nwa To: softrock40@yahoogroups.com Sent: Thursday, January 10, 2008 7:27 PM Subject: Re: [softrock40] Si570 PCB At 01:41 AM 1/9/2008, you wrote:
      Message 60 of 60 , Jan 10, 2008
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        ----- Original Message -----
        From: k5nwa
        Sent: Thursday, January 10, 2008 7:27 PM
        Subject: Re: [softrock40] Si570 PCB

        At 01:41 AM 1/9/2008, you wrote:

        Here's the schematic for an Si570 PCB I'm working on:

        http://www.leonheller.com/Si570/Si570.pdf

        The board includes a PIC16LF88 MCU, with a 3.3V LDO regulator, and has
        connectors for a rotary encoder and two pushbuttons. It's mostly
        surface-mount, and being single-sided will be easy to make at home. Size is
        1.325" x 2.15".

        73, Leon
        --

        Is that a ICSP connector to program the chip? Or is it some other standard.
        Yes, it's for an ICD 2 debugger/programmer.
         
        73, Leon
        --
        Leon Heller
        Amateur radio call-sign G1HSM
        Yaesu FT-817ND and FT-857D transceivers
        Suzuki SV1000S motorcycle
        leon355@...
        http://www.geocities.com/leon_heller
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