[sdiy] Static ADC and DAC recommendations?

[Scott Gravenhorst]

cheater cheater <cheater00 at gmail.com> wrote:
>Wait a sec guys - I thought the usual approach was folding converters.
>That is, you take the input signal, scale it to e.g. 0-1V, and see if
>it's the upper or lower half (so if it's positive then negative). You
>call that the msb, deduce 0.5V*logical value from the original signal,
>and you get something ranges from 0 to 0.5V. Then you scale that up
>twice to get a range 0-1V again, and repeat the whole process, getting
>the second bit, and so on. Only 8 comparators here, and, eh, how many
>transistors? I don't know off the top of my head. Why would that be so
>expensive to make in silicon?
>
>> If you do want a clockless converter, John Simonton wrote an 
>article in a long past polyphony on how to do this with LM339's 
>However while one LM339 will give you a 4 bit converter 
>
>I believe that's exactly what he's doing. I looked at doing this sort
>of thing with an LM339, but I just can't believe there isn't a chip
>out there that does this in integrated form. It seems like a
>no-brainer. I hope someone has a lead on that.. I *would* expect this
>sort of thing to be viewed as an anachronism nowadays, though, and
>probably limited to NOS or small-yield production runs.

I'm sure it's possible.  But there may not be an industry call for mass produced unclocked
ADCs.  Probably because the majority of applications want an ADC clock, so it gets put in
the silicon with the "stuff" required for ADC.

Someone else mentioned clocking a clocked ADC as fast as possible.  Maybe try to overclock
it if you're looking for dirt...

-- ScottG
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