[minima] Re: Si5351
- From: "Mac A. Cody" <maccody@xxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Wed, 29 Oct 2014 23:06:55 -0500
Joe,
I obtained one of the Si5341B devices (8 outputs with VCO input) awhile
back, but I have not done anything with it due to other activities.
I've studied the part specifications and I believe that the phase noise
may be significantly higher than that of the Si570. I just can't
quantify exactly how much more, though.
The Si570 specs quote a phase jitter of 0.62 ps typical for the CMOS
part. The Si5351 specs quote a period jitter and cycle-to-cycle jitter
of 50 to 70 ps, typical. These are apples-to-oranges comparisons, but
that is about a 100X difference. Even being generous and saying there
is only a 10X difference, it is still significant. I've downloaded
some of the Silicon Lab application notes on phase noise, but I've not
sorted through them yet. Still, Jason at NT7S.com has been using the
part in some of his QRP experiments. He thinks it might be a usable
part, but hasn't answered the phase noise issue either.
Hope that this helps.
73,
Mac AE5PH
On 10/29/2014 01:06 PM, Joe Rocci wrote:
Hi DuWayne!
I purchased the AdaFruit board with high hopes, but my initial
spectrum analyzer results are a bit disappointing. At first, the 2
active outputs (I'm using the NT7S 2-channel example code) were
crosstalking so that the Ch0 output was leaking into the Ch1 output
only 40 db down. I sort of cured that by reprogramming to use channels
0 and 2, which have more space between them on the chip. However, the
bigger problem is numerous spurs every couple Mhz only about 60-70 db
down. At first I thought this might be power supply noise from the
Arduino Nano that I'm running it with. I connected a lab supply to the
Si5351 board, but that didn't change anything. Then, thinking it might
be some digital noise from the Nano coming over on the I2C, I held the
reset button on the Nano, which I assume kills all I/O. That didn't
help either. I now think this might be some artifacts from the
fractional-N synthesis process, as the level of the spurs jumps up and
down several dB. If this truly is intrinsic in the part, it's almost a
deal-killer for anything but a novelty receiver.
I'd like to hear others' experiences.
Joe
W3JDR
----- Original Message -----
*From:*DuWayne KV4QB <mailto:duwayne@xxxxxxxx>
*To:*minima@xxxxxxxxxxxxx <mailto:minima@xxxxxxxxxxxxx>
*Sent:*Wednesday, October 29, 2014 11:11 AM
*Subject:*[minima] Re: Si5351
Just started to play with one of the Adafruit boards. Changed my
DDS board to use the 5351 board instead
The library from Jason seems to work well. Other than getting the
board to run I have not done anything else with it.
Don't know if I will use it on a Minima or will go with some other
design. Here is a shot of what I have so far.
DuWayne KV4QB
On 10/29/2014 8:28 AM, Joe Rocci wrote:
There was some talk here a while back about the Si5351, an
equivalent to the Si570 that has 3 programmable oscillators and
only costs a couple dollars. I just got an application board from
AdaFruit and fired it up to see how it performs. I have some
questions about spurious outputs that I'd like to discuss with
anyone who's using this part. If you have any experience with it,
please contact me directly(joeatroccisdotcom)
Joe
W3JDR
--
Of all the things I lost, I miss my mind the most.
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