[time-nuts] Slightly OT: interest in a four-output, ultra-low jitter, synthesizer block?
kb8tq at n1k.org
Thu Jan 25 14:07:51 EST 2018
> On Jan 25, 2018, at 2:02 PM, wb6bnq <wb6bnq at cox.net> 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.
With any non-integer PLL, the noise spreading performance is going to depend a bit on the phase detector
operating frequency. For integer division, things will be impacted, but not in the same way. The “ideal”
answer would be to feed the beast with a 50 MHz reference derived somehow from a 10 MHz source.
> 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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