[time-nuts] Slightly OT: interest in a four-output, ultra-low jitter, synthesizer block?
John Ackermann N8UR
jra at febo.com
Thu Jan 25 15:23:51 EST 2018
Hi Bill --
And that's exactly what I *don't* want to do. :-) The reason is that I
have several different projects in mind (and everyone else will have
their own requirements) and only want to deal with the difficult package
The idea is to make a minimal carrier to deal with the tiny part and
six-layer board. Then all the ancillary stuff (including the MCU that's
needed to program the chip) goes onto the board designed for that
project. This isn't intended to be a finished product, just a building
On 01/25/2018 03:12 PM, wb6bnq wrote:
> Hi John,
> Thanks for the response. Here is my 2 cents:
> Well, due to the level of difficulty in chip mounting, I would prefer to
> see a complete project. I.E., power supply for a single input of 12
> volts and regulators the necessary chip values, proper input protection
> for the 10 MHz input level and single ended outputs of the appropriate
> levels (I am assuming more than 3 volts) or an amplifier stage for
> arriving at such. Equally have RF connectors (SMA would be good) on the
> board perhaps.
> Of course as cheap as possible, hi hi. A carrier board arrangement
> would be useless to me. My application would be to provide signals for
> things like my Quicksilver SDR receiver, among other uses.
> If you are interested, I can show you a nice little ABS (I think) box
> that has EMI built-in that I used for a project that should be more than
> large enough for your needs.
> Thanks for reading,
> John Ackermann N8UR wrote:
>> Hi Bill --
>> I should have been more clear: this design will be for a simple case:
>> one reference clock input, four outputs. The chip can do all sorts of
>> fancy tricks, but I'm looking for a source of four low jitter outputs
>> derived from a 10 MHz external reference (not using crystal or
>> on-board oscillator). Many of the pins are unused in that configuration.
>> I'm not looking to make a universal carrier for the chip, but to meet
>> what I suspect is a common time-nut/ham radio desire for a clean
>> multi-channel synthesizer.
>> On 01/25/2018 02:02 PM, wb6bnq wrote:
>>> Hi John,
>>> After looking at the data sheet, it seems way more involved then just
>>> making a carrier board for it. Besides the power supply
>>> requirements, various design selections would dictate different
>>> circuit layouts for different purposes. Even trying to do a general
>>> purpose application would possibly require having several different
>>> output configurations and possibly a couple of input configurations
>>> as well. That would imply a rather detailed PCB and that chip
>>> package style is a serious pain in the ass for [what amounts to]
>>> hobbyists. So it would seem the logical course would be to do
>>> serious design application and see if an in-house component mounting
>>> job would be feasible.
>>> I notice that the data sheet says the jitter specs are only best when
>>> using The internal crystal oscillator frequency between 48 and 54
>>> MHz. It was unclear to me that the same would apply to using the
>>> non-crystal inputs.
>>> Perhaps you could indicate what you are attempting to do with it and
>>> how you are going to accomplish your goals ?
>>> John Ackermann N8UR wrote:
>>>> After the recent discussion about Silicon Labs clock generators, I
>>>> looked at their Si5340A part and think it will be useful for a ham
>>>> radio project I'm working on. While it can do other things, for my
>>>> use it would use a 10 MHz input clock and generate 4 independent
>>>> outputs in the range of 100 kHz to 1028 MHz. Its jitter is <100fs,
>>>> which translates to "not bad" phase noise. Here's the data sheet if
>>>> you're interested:
>>>> The challenge is that the chip is a 7x7 mm 44-QFN package and really
>>>> wants to be put on a six-layer circuit board. That's doable, but
>>>> challenging, for home assembly.
>>>> Rather than designing the chip into a larger circuit board, I'm
>>>> thinking of doing a small "carrier" board that would include just
>>>> the chip and critical bypass caps and have headers to plug into the
>>>> main board. Then, you could just drop the carrier into a
>>>> project-specific board and not have to worry about the complex
>>>> layout and mounting. I have a contract manufacturer who can build
>>>> these up, if there's enough quantity to justify the setup cost.
>>>> If you'd be interested acquiring in one or more of these, please
>>>> drop me a line off-list (jra at febo dot com). I don't think this
>>>> will be a TAPR project, but if there's enough interest to build 25
>>>> of these carriers, I can probably make that happen. And remember --
>>>> this is just the chip; you'll need to provide the rest of the circuit.
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