[sdiy] Another SSM2164 question

[Mattias Rickardsson]

I tried out the SSM2164 the other day, first neglecting the "great"
R+C recommendation in the datasheet, and got reeeally strange results.
The output seemed to have a strange negative offset that lead its own
life. It took a while before I realized that adding the R+C would make
everything work.

I don't have a good answer to your question, but I'd just assume that
the stated values give the best result, and I still haven't seen any
big problems in following them.

What's annoying me in the datasheet is "Figure 6. THD+N vs.
amplitude", where the horizontal axis shows a frequecy scale instead,
making the curves nearly worthless.

Revision 0 from 1994. Man, they must have had some really busy days
since then... or doesn't this nice chip sell enough? :-)

/mr


2008/8/12 Tom Wiltshire <tom at electricdruid.net>:
> Hi all,
>
> The subject says it all really. The VCAs in the SSM22164 require a 500R
> resistor and 560pF capacitor to ground on each VCA input, as well as a
> resistor to convert voltage to current (30K in the datasheet).
>
> Now, what I'd like to know is what do the 500R/560pF do and how are their
> values calculated? All the datasheet says about it is that "a 500R resistor
> in series with a 560pF capacitor must be added from each input to ground to
> ensure stability". Great.
>
> Practically, it seems you can vary the values a bit without incident (I've
> used 560R/470pF and nothing bad has happened) but it's a bit hard to know
> when you're not sure what they're supposed to prevent.
>
> The datasheet is at:
> http://www.analog.com/static/imported-files/data_sheets/SSM2164.pdf
>
> Thanks,
> Tom
>
>
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