Updated SSI2130 VCO Datasheet available...

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 08, 2020 3:46 am

BugBrand wrote:
Thu Oct 08, 2020 3:22 am
oldenjon wrote:
Wed Oct 07, 2020 1:18 pm
neil.johnson wrote:
Wed Oct 07, 2020 1:08 pm
Question for the audience at large: what topics, features, details or other information would you like to see in the SSI2130 data sheet?
Hi Neil, I'm curious if there is trick that can be used to get quadrature functionality from a pair of SSI2130. This would be very useful in a frequency shifter.
I like your thinking!

Good other comments in general - KSS & forestcaver especially.
If you can get the SSI2130 datasheet up to anywhere approaching the quality of the SSI2164 one!
Pretty darn gold-standard!
Thanks Tom! The SSI2164 datasheet improved over time, and you can see the contributions of several authors, not to mention the incredible AN-701 from Jeroen. I suspect the SSI2130 will be the same, with major revisions to begin with and tweaks later on.

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Thu Oct 08, 2020 5:39 am

neil.johnson wrote:
Thu Oct 08, 2020 3:46 am
Thanks Tom! The SSI2164 datasheet improved over time, and you can see the contributions of several authors, not to mention the incredible AN-701 from Jeroen. I suspect the SSI2130 will be the same, with major revisions to begin with and tweaks later on.

Neil
This is great to see... cheers Neil...

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 08, 2020 8:48 am

tom wrote:
Wed Oct 07, 2020 7:34 pm
total harmonic distortion of the sine shaper fed by the tri
About 0.3%.
tom wrote:
Wed Oct 07, 2020 7:34 pm
neil.johnson wrote:
Sun Oct 04, 2020 6:10 am
tom wrote:
Sun Oct 04, 2020 1:06 am
[...]The board should not heavily lower the specs of the IC.
Crosstalk of Sqare -> V+ seems to appear most likely with your layout.
The pinout has been carefully thought about. The most common use-cases have been designed in: triangle out to sine+ in, triangle out to PWM+ in, for example.
If the square out is not used it can be connected to ground.
I was refering to the layout of synthcube's board. We all know square bleed in synths and with the square out and +V as neighbours without screen, this most likely is going to happen!?
Same for the sine out. A very pure sine is key for the beauty of fm / quadrature ect.
Looking at Synthcube's layout I would guess very little capacitance between the square out and V+ traces (maybe a pF), and any there would be swamped by the 100nF decoupling capacitor, so the bleed will likely be extremely low. But the only way to know is to buy one and measure it. I look forward to your report :tu:

Likewise, the Sine Out is between VREF (constant DC, so no AC signal to couple) and MIXOUT, which if you're concerned about bleed you can feed into a virtual-earth summing node to keep it at or very close to 0V. Again, no AC voltage so very little bleed. And if I may ask, what do you mean by "very pure"? I don't think any of my test equipment has a scale marked in pure's... :hmm:

Of more concern will be the traces and circuits beyond this little board, and I don't think that is within the scope of Synthcube's board.

Cheers,
Neil
Last edited by neil.johnson on Mon Oct 12, 2020 4:48 pm, edited 1 time in total.
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 08, 2020 8:52 am

emmaker wrote:
Wed Oct 07, 2020 2:21 pm
One question I would have is if you have multiple SSI2130s can they share voltage regulators for V+, V- and Vref without any interaction/interference between the chips?

I'm also so assuming decent regulation is used here.

Thanks
Jay S.
Apply good board layout and grounding, tightly-placed and routed local decoupling, etc, and you should be ok :tu:
Although you don't need a regulator for V- I would be tempted to use a -5V regulator just to keep the rail noise away from the VCO.

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 08, 2020 9:20 am

forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
I really needed the additional info on power supply requirements/specs from the new draft datasheet that I believe is under development with Dan. That was the bit I was not getting until I read it.... and even there it was pretty much only needing to understand the negative rail’s regulation requirements. (From the current datasheet I couldnt work out whether I could just use a eurorack rail ie regulated -12v but subject to noise etc etc or whether more strict regulation was important to stability; from that info I’m going to be using a regulated, smoothed -5v supply)
This is a VCO. You want to keep the supply noise away from it as much as you can for best stability. Do not rely on PSRR. Best thing to do is sit it inside a regulated power domain at +/- 5V, local decoupling, good ground hygiene.
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
Also - as described above - the role of the central pad.
It is not connected to anything internal. Not even needed for thermal. But some folks like to solder it down to help on the production line.
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
Info on limits to some of the inputs eg pin 21 input but I can work it out from the reference design (but couldnt see it in the datasheet)
Likewise pin 18 - I’m assuming the voltage limit is the supply rails, but it’s not explicit (ie I’m not sure if it’s GND to +V or -V to +V, so I would protect vs -ve voltage but only because I cant tell from the datasheet).
Pin 21 is a current input. The eval board puts 5uA for normal operation, which is about typical. You can go higher, and the output frequency will go up, and vice versa. You can use it for traditional linear FM duties, or in conjuction with the external circuit for TZFM (and TZPM).
Pin 18 is really a logic input, with high and low states. All pins must be between V+ and V-. In this case the high threshold is about 2V, and low is about 0.8V or less (e.g., GND).

Cheers,
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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Thu Oct 08, 2020 9:38 am

neil.johnson wrote:
Thu Oct 08, 2020 9:20 am
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
I really needed the additional info on power supply requirements/specs from the new draft datasheet that I believe is under development with Dan. That was the bit I was not getting until I read it.... and even there it was pretty much only needing to understand the negative rail’s regulation requirements. (From the current datasheet I couldnt work out whether I could just use a eurorack rail ie regulated -12v but subject to noise etc etc or whether more strict regulation was important to stability; from that info I’m going to be using a regulated, smoothed -5v supply)
This is a VCO. You want to keep the supply noise away from it as much as you can for best stability. Do not rely on PSRR. Best thing to do is sit it inside a regulated power domain at +/- 5V, local decoupling, good ground hygiene.
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
Also - as described above - the role of the central pad.
It is not connected to anything internal. Not even needed for thermal. But some folks like to solder it down to help on the production line.
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
Info on limits to some of the inputs eg pin 21 input but I can work it out from the reference design (but couldnt see it in the datasheet)
Likewise pin 18 - I’m assuming the voltage limit is the supply rails, but it’s not explicit (ie I’m not sure if it’s GND to +V or -V to +V, so I would protect vs -ve voltage but only because I cant tell from the datasheet).
Pin 21 is a current input. The eval board puts 5uA for normal operation, which is about typical. You can go higher, and the output frequency will go up, and vice versa. You can use it for traditional linear FM duties, or in conjuction with the external circuit for TZFM (and TZPM).
Pin 18 is really a logic input, with high and low states. All pins must be between V+ and V-. In this case the high threshold is about 2V, and low is about 0.8V or less (e.g., GND).

Cheers,
Neil
Thanks Neil re: the supply - my thought processes were that the outputs were between 0 and Vref so I wasnt sure if the -ve supply had an effect on the vco core frequency stability or the noise of the outputs.... I dont know if anyone else would think like that but that was my reasoning....

Thanks for the info on pin 18 :-)

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Re: Updated SSI2130 VCO Datasheet available...

Post by BugBrand » Fri Oct 09, 2020 3:30 am

I think a diagram showing waveform phase relationships would be helpful - inc what happens when strobe or soft-sync are implemented.
I've got a reasonable feel from the datasheet & discussions but having it painted out would, I think, be clearer & very helpful!

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 09, 2020 3:46 am

BugBrand wrote:
Fri Oct 09, 2020 3:30 am
I think a diagram showing waveform phase relationships would be helpful - inc what happens when strobe or soft-sync are implemented.
I've got a reasonable feel from the datasheet & discussions but having it painted out would, I think, be clearer & very helpful!
:tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 16, 2020 5:11 am

A little something I took the other day...
2130-fm.jpg
Neil (feeling a bit of a tease today :oops: )
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Re: Updated SSI2130 VCO Datasheet available...

Post by lickspittle » Fri Oct 16, 2020 8:44 am

Through zero FM, Neil? Very impressive.

It'd be nice to see something similar for hard and soft sync, if you have time.

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 16, 2020 11:01 am

Hard sync just resets the triangle to 0, whereas soft sync changes direction but only has an effect when the triangle is falling.

I can only do so much teasing in one day ;)

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Re: Updated SSI2130 VCO Datasheet available...

Post by lickspittle » Fri Oct 16, 2020 11:42 am

Thanks Neil. That suggests interesting possibilities if you trigger the sync using a modulated pulse wave.

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 16, 2020 3:32 pm

Oh yes, there are many interesting things you can do with this fascinating device.

Exciting times ahead!

Cheers
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Re: Updated SSI2130 VCO Datasheet available...

Post by J3RK » Mon Oct 19, 2020 1:04 pm

Very nice! Moving right now, but hope to start playing with these soon.

Neil, you need to get a 200 MegaPures Pure-O-Scope as soon as possible. It's an essential piece of test equipment.
Are you lemon? Does your head come to a nub?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Mon Oct 19, 2020 1:49 pm

J3RK wrote:
Mon Oct 19, 2020 1:04 pm
Neil, you need to get a 200 MegaPures Pure-O-Scope as soon as possible. It's an essential piece of test equipment.
Oooh really? Better than my Tek???!!! :hihi:

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Re: Updated SSI2130 VCO Datasheet available...

Post by Tonescape » Wed Oct 28, 2020 8:56 am

neil.johnson wrote:
Thu Oct 08, 2020 9:20 am
forestcaver wrote:
Wed Oct 07, 2020 1:33 pm
I really needed the additional info on power supply requirements/specs from the new draft datasheet that I believe is under development with Dan. That was the bit I was not getting until I read it.... and even there it was pretty much only needing to understand the negative rail’s regulation requirements. (From the current datasheet I couldnt work out whether I could just use a eurorack rail ie regulated -12v but subject to noise etc etc or whether more strict regulation was important to stability; from that info I’m going to be using a regulated, smoothed -5v supply)
This is a VCO. You want to keep the supply noise away from it as much as you can for best stability. Do not rely on PSRR. Best thing to do is sit it inside a regulated power domain at +/- 5V, local decoupling, good ground hygiene.

Cheers,
Neil
A side question: What do you prefer to use these days for regulated +/-5V power? Thanks ;)
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Re: Updated SSI2130 VCO Datasheet available...

Post by BugBrand » Wed Oct 28, 2020 9:42 am

Neil wrote earlier:
" Personally I prefer to wrap the VCO in a nice little filtered power environment so a 78L05 and a 79L05, plus a TL431 for Vref, and you're sorted "

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Re: Updated SSI2130 VCO Datasheet available...

Post by Tonescape » Wed Oct 28, 2020 9:48 am

BugBrand wrote:
Wed Oct 28, 2020 9:42 am
Neil wrote earlier:
" Personally I prefer to wrap the VCO in a nice little filtered power environment so a 78L05 and a 79L05, plus a TL431 for Vref, and you're sorted "
Arh, sorry, missed that. Thank you :party:
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 29, 2020 10:41 am

:tu:
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Oct 29, 2020 5:41 pm

oldenjon wrote:
Wed Oct 07, 2020 1:18 pm
Hi Neil, I'm curious if there is trick that can be used to get quadrature functionality from a pair of SSI2130. This would be very useful in a frequency shifter.
neil.johnson wrote:
Thu Oct 08, 2020 3:44 am
Tricky to get a seamless sync between the two oscillators. Have you considered a voltage-controlled all-pass filter to provide a 90 degree phase shift that tracks the VCO? You could do it with 1/4 of an SSI2164 and a couple of op-amps.
Neil
Something like this:


Details to come in the SSI2130 datasheet.

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Re: Updated SSI2130 VCO Datasheet available...

Post by bomby » Fri Oct 30, 2020 2:03 am

I've always figured QFN parts were something I'd never use, but this chip got me interested and I'm pretty sure I managed to solder one of these successfully on my first try with a stencil, solder paste, and hot air gun. I've soldered plenty of SOIC, 0805, and similarly-sized SMT but never soldered a QFN part before, and I've only ever successfully soldered a handful of QFPs. I wouldn't describe it as easy by any means, but if you have a hot air gun it's definitely doable even if you're not an expert. Aligning the stencil was the most painful part. After the first go with the air gun most sides looked something like the top side here:

Image

I tackled a couple of those spots by just hitting it with the very corner of some solder braid, but I was able to get most of them fixed by just putting a freshly-cleaned chisel tip on them and dragging outward. I only soldered it to a very basic breakout, so I don't have anything to say about its functionality at this point (and I can't be 100% sure it works correctly, but everything looks good through through a jeweler's loupe). Just posting this for anyone like me out there who's on the fence about whether something like this would be impossible for them:

Image

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Re: Updated SSI2130 VCO Datasheet available...

Post by BugBrand » Fri Oct 30, 2020 3:36 am

neil.johnson wrote:
Thu Oct 29, 2020 5:41 pm
Something like this:


Details to come in the SSI2130 datasheet.

Neil
Great - both the video and the details to come!
Quadrature via all-pass ---- this sounds an interestingly simple solution that hasn't really been seen before!

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 30, 2020 1:15 pm

bomby wrote:
Fri Oct 30, 2020 2:03 am
I've always figured QFN parts were something I'd never use, but this chip got me interested and I'm pretty sure I managed to solder one of these successfully on my first try with a stencil, solder paste, and hot air gun. I've soldered plenty of SOIC, 0805, and similarly-sized SMT but never soldered a QFN part before, and I've only ever successfully soldered a handful of QFPs. I wouldn't describe it as easy by any means, but if you have a hot air gun it's definitely doable even if you're not an expert. Aligning the stencil was the most painful part. After the first go with the air gun most sides looked something like the top side here:

Image

I tackled a couple of those spots by just hitting it with the very corner of some solder braid, but I was able to get most of them fixed by just putting a freshly-cleaned chisel tip on them and dragging outward. I only soldered it to a very basic breakout, so I don't have anything to say about its functionality at this point (and I can't be 100% sure it works correctly, but everything looks good through through a jeweler's loupe). Just posting this for anyone like me out there who's on the fence about whether something like this would be impossible for them:

Image
Looks great! :tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Oct 30, 2020 1:19 pm

BugBrand wrote:
Fri Oct 30, 2020 3:36 am
neil.johnson wrote:
Thu Oct 29, 2020 5:41 pm
Something like this:


Details to come in the SSI2130 datasheet.

Neil
Great - both the video and the details to come!
Quadrature via all-pass ---- this sounds an interestingly simple solution that hasn't really been seen before!
Thanks Tom! You can call it the "Johnson Oscillator" or "Johnson Configuration" :yay:

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