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Re: Si570 frequency ranges

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  • tom_iphi
    Hi all, I have tested an LVDS connected to a spectrum analyzer on my USB controller and didn t see any problems in the whole range up to 1.4GHz. Of course, the
    Message 1 of 7 , Aug 31 11:02 PM
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      Hi all,

      I have tested an LVDS connected to a spectrum analyzer on my USB
      controller and didn't see any problems in the whole range up to
      1.4GHz. Of course, the spec gaps are there. They are due to the VCO
      range and possible divider combinations. I don't understand, why
      SILabs don't spec down to 3.5MHz, as a simple calculation reveals,
      that this is possible without running the VCO outside spec.

      I would assume, that the DSPLL core is identical for all SI570s,
      likely CMOS for all. I remember from a visit to SiLabs some time ago,
      that they stated, they would do all in CMOS because of lower cost and
      they were proud that they could do things in CMOS that other people
      couldn't. I also assume, that there are just different output buffers
      for the different types. This would also make sense from a
      development and production cost point of view.

      BTW: If you hold a fast CMOS buffer close to threshold it is likely
      to oscillate.

      73's Tom DG8SAQ

      --- In softrock40@yahoogroups.com, "Kees & Sandy" <windy10605@...>
      wrote:
      >
      > What I see using a "CAC000141G" CMOS part (the LVDS part will be
      the same) stepped at 10Khz increments is a nice sine wave at 473Mhz
      (scope indicates 469.4Mhz). Tuning beyond that shows a very unstable
      56Mhz (according to the scope) "square" wave (sound like a familiar
      frequency ?) of much greater amplitude which then changes to an
      unstable ~113-130Mhz sine wave. This is when the part has definitely
      lost lock. At 486Mhz the output returns to a nice sine wave.
      > Again, this is just for interest and well beyond where the part is
      spec'd. And well beyond the frequency range where nearly all people
      would use a "C" speed part. The Silicon Labs spec sheet for "A" speed
      parts shows 10-945Mhz, 970-1134Mhz, and 1213-1417.5Mhz. Please note
      the frequency "gaps" where it is spec'd to NOT be operational.
      > 73 Kees K5BCQ
      >
      > -- "John H. Fisher" <k5jhf@...> wrote:
      >
      > This might be considered inconclusive because you didn't test with
      > Kees's Si570 and Kees didn't test with your Si570. So you can't say
      > it's the controller. It could still be that some Si570's work better
      > than others.
      >
      > Regards,
      > John
      >
      > --- In softrock40@yahoogroups.com, "jhops99" <jhops@> wrote:
      > >
      > > --- In softrock40@yahoogroups.com, "Kees" <windy10605@> wrote:
      > > >
      > > > I previously tested a Si570 LVDS part which is a "BBC000141G"
      which
      > > > means 3.3V LVDS, 10-280Mhz supported (correction from before),
      > > > 90ppm/V tuning slope. I see basically the same results 3.5Mhz
      to
      > > > 473Mhz looks fine, some "default" frequency from 474Mhz to
      485Mhz, OK
      > > > from 486Mhz to 566Mhz, some "default" frequency from 567Mhz to
      > > > 607Mhz, OK from 608Mhz to 709Mhz.
      > > >
      > > >
      > > > 73 Kees K5BCQ
      > > >
      > > Kees,
      > > Tried the bad frequency ranges on my BBC000141G but using the UBW
      > > Kenwood Si570 control software and didn't see any problem. Tried
      some
      > > 10kHz steps in each range.
      > >
      > > 73 Joe WB8DNO
      > >
      >
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