Updated SSI2130 VCO Datasheet available...

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neil.johnson
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Sun Nov 15, 2020 2:28 pm

I strongly recommend the circuit from the data sheet, including the component values. Also perhaps a bit of positive feedback around the comparator.

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Re: Updated SSI2130 VCO Datasheet available...

Post by DozenCrows » Sun Nov 15, 2020 4:37 pm

I tried a different modulation source that appeared to put out a more symmetric sine wave - and that made quite an improvement. I also tried AC coupling the linear FM input, and that got rid of the pitch shift also. So I think an offset in the original modulator output is at least partly to blame. I still get beating, but I think that's now down to any difference in modulator and carrier pitch: e.g. arising from a little analogue drift. It can be tuned out.

I plan to try the data sheet circuit and see how it compares - thank you Neil!

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Re: Updated SSI2130 VCO Datasheet available...

Post by BugBrand » Mon Nov 16, 2020 11:14 am

IMG_20201116_160155.jpg
Thumbsup! Mess of solderpaste+flux but seemed to tidy up ok with more flux & applying solder-braid to the sides.

Couple of low resistance measured but not reporting shorts.. so a little curious - could anyone perhaps measure the following [measured before fitting any other components]:

pin21 to 0V (hftbias pin20) - 833ohms
pin30 (pulse) to pin29 (saw) - 1011ohms
pin30 (pulse) to pin31 (PWM- // connected too to pin1 tri) - 945ohms
pin1 (tri) to pin2 (sin_in+) - 1038 ohms
pin3 (sin in-) to pin4 (aux in 1) - 997 ohms
pin7 (ExpFrq) to pin8 (v-) - 645ohms
pin9 (TriMixLvl) to pin10 (sawlvl) - 1055ohms
pin14 (cap) to pin15 (0V) - 815ohms

Having never worked with something so tiny (nor much at such low voltages) I don't know whether such readings suggest the soldering isn't quite there!

**EDIT --- probably scratch that! Did another pass of braid cleaning which seemed to clean some - but also tried using the DMM (Keithley) from continuity test to regular ohm-meter. Now measuring any 'suspects' are actually at least 50K (whereas showing the above ohm values when set to continuity) - so I think this was a false alarm ;)

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Tue Nov 17, 2020 1:54 pm

Quick question - what is the best thing to do with unused mix inputs and mix output ? I guess the inputs should be connected to ground but should the mix out be connected via 5k to ground or can it be left floating ? I’m guessing to GND. Likewise, if any waveforms outputs are unused, what is the best thing to do with them?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Wed Nov 18, 2020 6:23 am

You can leave any unused mixer connections (inputs and outputs) unconnected.
Same for waveform outputs.

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Wed Nov 18, 2020 8:33 am

Thanks Neil. Also, are there any issues with -ve voltage (and current) at pins 6 and 7 ?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Wed Nov 18, 2020 8:46 am

forestcaver wrote:
Wed Nov 18, 2020 8:33 am
Thanks Neil. Also, are there any issues with -ve voltage (and current) at pins 6 and 7 ?
Pin 6 is a current output, you can pull it down to V- with a resistor. Pin 7 is a ground-referenced current input which only responds to positive current. Any connection to these pins should be through resistors. What sort of circuit are you thinking about?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Wed Nov 18, 2020 8:47 am

And it goes without saying (I hope!) that you must never take a pin outside of the chip's power pins. Otherwise :deadbanana:

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Wed Nov 18, 2020 9:11 am

neil.johnson wrote:
Wed Nov 18, 2020 8:46 am
forestcaver wrote:
Wed Nov 18, 2020 8:33 am
Thanks Neil. Also, are there any issues with -ve voltage (and current) at pins 6 and 7 ?
Pin 6 is a current output, you can pull it down to V- with a resistor. Pin 7 is a ground-referenced current input which only responds to positive current. Any connection to these pins should be through resistors. What sort of circuit are you thinking about?

Neil
Thanks - nothing too exciting - just a eurorack full-fat vco. But I’m just planning edge cases and making sure inputs are protected properly. Was just making sure that even if I patched +/-12v to a v/oct input (buffered etc) and then through the 50k resistor to get 20uA/Oct at pin 7 and through the refererence design HFT trim at pin 6, that I wouldnt be damaging the ssi2130. Was going round in circles a bit and unsure if I needed to ensure the inputs were only +ve

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Wed Nov 18, 2020 9:17 am

Best practice is to condition and limit all inputs before they get anywhere near internal circuits. But that applies to all design, not just the SSI2130.

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Re: Updated SSI2130 VCO Datasheet available...

Post by julios » Fri Nov 20, 2020 4:52 am

I have the VCO working and it's amazing,the TZ FM sounds really nice, congratulations to SSI!
Thanks Neil, you've been very helpfull!

Now a question for my next PCB revision:
How would one add both linear FM and TZ Fm?
is it a matter o just sending a scaled signal with a parallel 500k through pin 21?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Nov 20, 2020 4:58 am

julios wrote:
Fri Nov 20, 2020 4:52 am
I have the VCO working and it's amazing,the TZ FM sounds really nice, congratulations to SSI!
Thanks Neil, you've been very helpfull!

Now a question for my next PCB revision:
How would one add both linear FM and TZ Fm?
is it a matter o just sending a scaled signal with a parallel 500k through pin 21?
TZFM is a superset of linear FM, so just add an offset into the TZFM input. If your TZFM signal is only positive then they are exactly the same. Think of TZFM as linear FM that also allows you to go into negative frequencies.

If you inject a separate current into pin 21 as you suggest, then you will not get TZFM because the comparator will flip when the oscillator is not at DC.

Just add another input in parallel with the TZFM input and call it "Linear FM" :tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by julios » Fri Nov 20, 2020 7:30 am

neil.johnson wrote:
Fri Nov 20, 2020 4:58 am
TZFM is a superset of linear FM, so just add an offset into the TZFM input. If your TZFM signal is only positive then they are exactly the same. Think of TZFM as linear FM that also allows you to go into negative frequencies.

If you inject a separate current into pin 21 as you suggest, then you will not get TZFM because the comparator will flip when the oscillator is not at DC.

Just add another input in parallel with the TZFM input and call it "Linear FM" :tu:

Neil
ok, let me know if i'm getting it right:

Considering the datasheet TZ input schematic, if i use a dpdt switch to switch the VRef from 2.5V to 5V and the signal input resistor 20k to 40k would this turn the input into a linear FM input?
This way the input signal is scaled to not cross the 2.5V vref, not triggering the comparator.

I'm i thinking right?

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Nov 20, 2020 7:49 am

julios wrote:
Fri Nov 20, 2020 7:30 am
ok, let me know if i'm getting it right:

Considering the datasheet TZ input schematic, if i use a dpdt switch to switch the VRef from 2.5V to 5V and the signal input resistor 20k to 40k would this turn the input into a linear FM input?
This way the input signal is scaled to not cross the 2.5V vref, not triggering the comparator.

I'm i thinking right?
What input signal range do you want to support? The TZFM input is already a linear FM input. For example, if you want to support an input range of +/- 5V then I would simply add another input but with a 40k resistor and call it "LIN FM IN".

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Re: Updated SSI2130 VCO Datasheet available...

Post by Ayeh » Sun Nov 22, 2020 7:15 am

Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Sun Nov 22, 2020 6:30 pm

Ayeh wrote:
Sun Nov 22, 2020 7:15 am
Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
The heart of the SSI2130 is a triangle oscillator that goes between 0V and 2.5V. Hard Sync resets the triangle to 0V. If you then shift and scale the triangle wave then you will find it resets to the negative/lowest point. Same result if you use the sine shaper. Unfortunately there is no way (yet) of resetting to any other position. It's something I am working on as several folks have asked about it.

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Re: Updated SSI2130 VCO Datasheet available...

Post by Ayeh » Mon Nov 23, 2020 8:16 am

neil.johnson wrote:
Sun Nov 22, 2020 6:30 pm
Ayeh wrote:
Sun Nov 22, 2020 7:15 am
Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
The heart of the SSI2130 is a triangle oscillator that goes between 0V and 2.5V. Hard Sync resets the triangle to 0V. If you then shift and scale the triangle wave then you will find it resets to the negative/lowest point. Same result if you use the sine shaper. Unfortunately there is no way (yet) of resetting to any other position. It's something I am working on as several folks have asked about it.

Neil
Ok, that makes sense.

Does it mean the IC will have rev2? or is it something that can be achieved with external circuitry?
Thank you for the information

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Mon Nov 23, 2020 8:52 am

Ayeh wrote:
Mon Nov 23, 2020 8:16 am
neil.johnson wrote:
Sun Nov 22, 2020 6:30 pm
Ayeh wrote:
Sun Nov 22, 2020 7:15 am
Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
The heart of the SSI2130 is a triangle oscillator that goes between 0V and 2.5V. Hard Sync resets the triangle to 0V. If you then shift and scale the triangle wave then you will find it resets to the negative/lowest point. Same result if you use the sine shaper. Unfortunately there is no way (yet) of resetting to any other position. It's something I am working on as several folks have asked about it.

Neil
Ok, that makes sense.

Does it mean the IC will have rev2? or is it something that can be achieved with external circuitry?
Thank you for the information
External circuitry.

Neil
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Re: Updated SSI2130 VCO Datasheet available...

Post by DozenCrows » Mon Nov 23, 2020 10:21 am

More on TZFM - I built the datasheet circuit to compare to the precision rectifier version I posted about earlier, and they pretty much work the same. As in I got the same minor detune issue with my 3340 modulator, fixed with AC coupling. I think that backs up my hypothesis that asymmetry in the 3340 circuit's output together with some slight tuning drift were behind it.

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Mon Nov 23, 2020 11:02 am

DozenCrows wrote:
Mon Nov 23, 2020 10:21 am
More on TZFM - I built the datasheet circuit to compare to the precision rectifier version I posted about earlier, and they pretty much work the same. As in I got the same minor detune issue with my 3340 modulator, fixed with AC coupling. I think that backs up my hypothesis that asymmetry in the 3340 circuit's output together with some slight tuning drift were behind it.
To be honest that is to be expected, as the FM circuit is all DC-coupled, so any Dc component is going to introduce a tuning error. AC coupling (which turns it into PM) fixes that. And then you have recreated Yamaha "FM" :tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by Ayeh » Mon Nov 23, 2020 6:03 pm

neil.johnson wrote:
Mon Nov 23, 2020 8:52 am
Ayeh wrote:
Mon Nov 23, 2020 8:16 am
neil.johnson wrote:
Sun Nov 22, 2020 6:30 pm
Ayeh wrote:
Sun Nov 22, 2020 7:15 am
Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
The heart of the SSI2130 is a triangle oscillator that goes between 0V and 2.5V. Hard Sync resets the triangle to 0V. If you then shift and scale the triangle wave then you will find it resets to the negative/lowest point. Same result if you use the sine shaper. Unfortunately there is no way (yet) of resetting to any other position. It's something I am working on as several folks have asked about it.

Neil
Ok, that makes sense.

Does it mean the IC will have rev2? or is it something that can be achieved with external circuitry?
Thank you for the information
External circuitry.

Neil
That´s great!
Thanks

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Tue Nov 24, 2020 2:35 pm

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Re: Updated SSI2130 VCO Datasheet available...

Post by BugBrand » Tue Nov 24, 2020 4:28 pm

^ha
Neil posted an updated datasheet on SIDY - http://www.soundsemiconductor.com/downl ... asheet.pdf
It has three new example circuits - very nice! 4QuadrantMultiplier, 3-way-waveform-crossfader & (tracking) quadrature.
Damn good!

[even if I did fail to get my own test board working today - grr]

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Tue Nov 24, 2020 4:41 pm

Ha ! I thought I’d finished my design - was getting close to sending off for pcbs !!!
Thanks for that @BugBrand ! Back to the design stage with this excellent datasheet !! :-)

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Re: Updated SSI2130 VCO Datasheet available...

Post by lemberski » Mon Nov 30, 2020 3:12 am

neil.johnson wrote:
Mon Nov 23, 2020 8:52 am
Ayeh wrote:
Mon Nov 23, 2020 8:16 am
neil.johnson wrote:
Sun Nov 22, 2020 6:30 pm
Ayeh wrote:
Sun Nov 22, 2020 7:15 am
Hello guys, when sending a trigger to hard sync is it possible to reset the waveform from 0V and not from negative like the pic??
The heart of the SSI2130 is a triangle oscillator that goes between 0V and 2.5V. Hard Sync resets the triangle to 0V. If you then shift and scale the triangle wave then you will find it resets to the negative/lowest point. Same result if you use the sine shaper. Unfortunately there is no way (yet) of resetting to any other position. It's something I am working on as several folks have asked about it.

Neil
Ok, that makes sense.

Does it mean the IC will have rev2? or is it something that can be achieved with external circuitry?
Thank you for the information
External circuitry.

Neil
Here the phase relationships as I understand it (bottom for tri core):
IMG_20201130_084627.png
Phaseshifting the ramp/saw by 90°with this circuit (simplified version of Hutchins "sawanimator") and folding into triangle would also give quadrature output relative to the triangle core (and taking care of the switching glitches):
sawshaper_Elektor_1982-09.pdf
(553.21 KiB) Downloaded 14 times

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