Re: [time-nuts] SI5328

[Attila Kinali]

On Mon, 22 Jan 2018 08:18:29 -0600
"Chris Caudle"  wrote:

> The DSP loop filter gives a really wide range of loop bandwidth, down to
> fractional Hz for some parts.  Using a DDS for the VCO gives a lot of
> flexibility in output frequency selection, but means that there can be
> problems with  spurs.  Part of the SiLabs secret sauce is supposed to
> reduce spurs compared to a simpler NCO implementation, but I don't think
> you can eliminate spurs entirely with any kind of DDS based design.

The secret sauce is not so secret, actually. It's just how you
build a higher order delta-sigma modulator. Most PLL implementations
still use a 1st-order modulator, with the well known spur problem
(they arise from the "idle-tone" problem in delta-sigma modulators)
The "low-spur" fractional PLLs use a 2nd or 3rd order modulator.
There has been some research in the last decade or so on how to
reduce those spurs further (mostly using even higher order and some
times using tricks like actively introducing errors to spread the
spurs) and most of it can be found online on IEEE and the like.

For a gentle introduction, have a look at Schreier, Pavan and Teme's
book "Understanding Delta Sigma Data Converters." 

I find the idea of using two cascaded control loops neat. It helps
to control erros (aka noise) contributed by the second (inner) loop.
However, how this reduces suceptibility to vibration, I am not entirely sure.
The reason why most people do not do this is easily explained: it's more
difficult to get a stable system with nested loops, as the conditions
for stability becomes more complex than with just a standard, straight
forward PID loop.

Attila Kinali


-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] SI5328

[J. Grizzard]

There are many small volume assmebly houses available. But the problem
is that you will have setup costs in the order of at least 100-300€,
even if you go to China. So, producing lots of less than 10 is not economical,
probably should aim for 100.


I recently ran across MacroFab (https://macrofab.com/), who can do small 
orders (quantity: 1) of boards, assembled, for what seems like 
reasonable prices. I haven't actually used them, but I did run a recent 
board through their process (except for actually ordering), and they 
came out with a price of ~$170 for a board that cost me ~$100 to 
assemble myself ($35 for board, ~$65 for BoM), so that's not too bad. I 
imagine the numbers would be smaller for simpler boards (this one is ~80 
components and pretty big -- 110mm x 60mm). The price came down pretty 
quick for quantity 3 or 5 or 10, though I don't remember the specifics.


The downside being that you have to be able to upload part-placement 
info that is actually correct. Most layout programs don't seem to have 
an issue generating it, though -- I just uploaded my gerbers and my 
KiCad PCB file and it just ran with it.


FWIW, it's not that hard to do even fine-pitch SMD stuff onesself. 
There's a little bit of startup cost (you really want to build a proper 
reflow toaster), but with high quality PCBs available via OSHPark (and 
fast! My *four layer* board was ~10 days), and quality stencils 
available via OSHStencils, doing even fine-pitch SMD work at home is 
surprisingly easy. In most simple cases, you don't even need the stencils...


-j
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Re: [time-nuts] SI5328

[Attila Kinali]

Hoi Bert,

On Mon, 22 Jan 2018 06:34:42 -0500
ew via time-nuts  wrote:

> In my opinion the SI 5328 is worth looking at for time nut application, like 
> offset frequency. My problem is solder ability. Does any one know a source
> for an evaluation board or as an alternative a source that would do a small
> volume assembly?

As others have written, an eval board is available.

There are many small volume assmebly houses available. But the problem
is that you will have setup costs in the order of at least 100-300€,
even if you go to China. So, producing lots of less than 10 is not economical,
probably should aim for 100.

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] SI5328

[Robert LaJeunesse]

It might be possible to hand solder the 36-pin 0.5mm pitch QFN to this 
Schmartboard product:
http://schmartboard.com/schmartboard-ez-qfn-36-pins-5mm-pitch-32-pins-65mm-pitch-2-x-2-grid-202-0043-01/

One question is would the die attach pad, which apparently needs grounding, get 
enough heat sinking.

Bob L.

> Sent: Monday, January 22, 2018 at 6:34 AM
> From: "ew via time-nuts" <time-nuts@febo.com>
> To: time-nuts@febo.com
> Subject: [time-nuts] SI5328
>
> In my opinion the SI 5328 is worth looking at for time nut application, like 
> offset frequency. My problem is solder ability. Does any one know a source 
> for an evaluation board or as an alternative a source that would do a small 
> volume assembly?
> 
> Bert Kehren
> ___
> time-nuts mailing list -- time-nuts@febo.com
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> 
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Re: [time-nuts] SI5328

[Mark Goldberg]

On Mon, Jan 22, 2018 at 4:34 AM, ew via time-nuts 
wrote:

> In my opinion the SI 5328 is worth looking at for time nut application,
> like offset frequency. My problem is solder ability. Does any one know a
> source for an evaluation board or as an alternative a source that would do
> a small volume assembly?
>
> Bert Kehren
>


There is a development board. It is about $200. Search for SI5328-EVB from
the usual places.

https://octopart.com/search?q=si5328-evb=0

You can download the support software and try it out ahead of time from
here:

https://www.silabs.com/products/development-tools/timing/clock/si5328-evb-development-kit

There have been several discussions about it as part of Leo Bodanar's
GPSDOs. Search the recent archives of this list:

https://www.mail-archive.com/search?l=time-nuts%40febo.com=si5328

Mark
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Re: [time-nuts] SI5328

[Christoph Kopetzky]

Hello,

here you can find the source of the development board with the Silicon 
price and the neccessary software package:


https://www.silabs.com/products/development-tools/timing/clock/si5328-evb-development-kit

-
Chris

Am 22.01.2018 um 12:34 schrieb ew via time-nuts:

In my opinion the SI 5328 is worth looking at for time nut application, like 
offset frequency. My problem is solder ability. Does any one know a source for 
an evaluation board or as an alternative a source that would do a small volume 
assembly?

Bert Kehren
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Re: [time-nuts] SI5328

[Christoph Kopetzky]

Bert,

please look at the following manual:
https://www.silabs.com/documents/public/user-guides/Si5328EVB.pdf

-
Chris

Am 22.01.2018 um 12:34 schrieb ew via time-nuts:

In my opinion the SI 5328 is worth looking at for time nut application, like 
offset frequency. My problem is solder ability. Does any one know a source for 
an evaluation board or as an alternative a source that would do a small volume 
assembly?

Bert Kehren
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Re: [time-nuts] SI5328

[Chris Caudle]

On Mon, January 22, 2018 6:42 am, Hal Murray wrote:
> Does anybody know what's in the DSPLL box?

Basically a PLL implemented with some kind of DDS for the VCO and DSP for
the loop filter.

https://www.silabs.com/documents/public/white-papers/Silicon-Labs-Next-Generation-DSPLL-Technology-White-Paper---June-2015.pdf

The DSP loop filter gives a really wide range of loop bandwidth, down to
fractional Hz for some parts.  Using a DDS for the VCO gives a lot of
flexibility in output frequency selection, but means that there can be
problems with  spurs.  Part of the SiLabs secret sauce is supposed to
reduce spurs compared to a simpler NCO implementation, but I don't think
you can eliminate spurs entirely with any kind of DDS based design.

-- 
Chris Caudle




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Re: [time-nuts] SI5328

[Hal Murray]

Does anybody know what's in the DSPLL box?

It may be in the data sheet(s), but I haven't found it.


-- 
These are my opinions.  I hate spam.



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[time-nuts] SI5328

[ew via time-nuts]

In my opinion the SI 5328 is worth looking at for time nut application, like 
offset frequency. My problem is solder ability. Does any one know a source for 
an evaluation board or as an alternative a source that would do a small volume 
assembly?

Bert Kehren
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