[sdiy] 2164 stability values

Neil Johnson neil.johnson71 at gmail.com
Sat Jun 30 12:36:15 CEST 2018

Hi Sam,

> You should not change the phase compensation network.
> I made a rough simulation of the internal circuit of 2164.  It is not reliable
> for design but useful to qualitative understanding.  It showed that the input
> resistor (30k) has almost no influence on the stability.
> I tested 10k to 100k and the difference is just the gain which is reverse
> proportional to the resistor value.
> Stability (peak frequency and the height in the frequency response)
> varies with gain CV.  I guess the compensation network covers all the
> ranges as far as the input resistor value is over 10k.

Be aware that rough simulations rarely include all the parasitics and
actual silicon behaviour that results in actual performance, and in
particular the effects of phase shifts and parasitic capacitances that
cause poles in the response.

In this case, a couple of us on this list have been working with Sound
Semiconductor Inc (SSI) who have released their own version of the
2164 in the guide of the SSI2164.  As they have the original SSM2164
designer on their team the investigation into the tuning of the
compensation network has been most interesting and fruitful.  For
example, here is the latest version of the SSI2164 datasheet:

Note the comment that for input resistors of 10k or below they say
that you need to change the input compensation network.  I have more
detailed information to hand which I believe will be going into the
next version of the datasheet.


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