Re: Simple multi-channel serial ADC (8-ch)?

Marte Schwarz wrote:

Hi Jörg,

7022 is with $4 delivering 10 AD ports with 12 bit.

More like $5/1k, at least in the US:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=130267&Site=US&Cat=33358756


$ 3.98 from http://www.analog.com/en/subCat/0,2879,762%255F%255F0%255F%255F0%255F,00.html


Err, I clicked on it. Seems they don't have 1000 but only 490. They want $4.52 per chip if you buy them all.


But not that much stock which always has me a bit worried. You couldn't even buy 1000 of them for that price right now because they only have 597. Some of the non-stocked versions show this little note: "Obsolete item; call Digi-Key for more information."


May be but this is only a example. Guess your very special AD wouldn't be in stock too.


I am going to use something like the TLV1548, around $3-4. Plenty in stock, there are many similar ones. If the SW guys don't like the initialization chat I might spoof it like I described before. But maybe they don't mind.


the ADuC7022 may not be the cheapest solution, Atmel may have cheaper ones, or Reneas, or...


May be you want to use a very cheap ATtiny with a 4067 as Mux? I'm sure this isn't to beat. for low data rate you can create your own quad slope AD using the cheapest controller to be found.


Slope might be a bit too slow because I need eight channels and SW guys usually prefer to read those in one fell swoop.


The Analog MicroConverters do really have excelent AD-units. That's what I know, this is what you didn't guess, me too, but we tested it.

AD is known for analog excellence. Did you do a hard test down to the noise level against a stand-alone ADC? And look at clock beats and stuff?


I saw the sample results from 1 Hz full scale sine wave without a plane or such special features just given to the minikit sampled there and transmitted this online with 2 kSps over UART (UART-USB-Bridge - Yes powered from USB! but with onboard 3V3 regulator). It looks fine without missing codes, only a few toggles around the last bit. In my view a very good result. I didn't expect more than 9 bits.


That is indeed quite good.


The other issue is that it's difficult to find local coders that know this uC.


It is a ARM7 controller and the only thing you need is the data*** (handy vs 100 pages) and little knowledge of Ansi C. There are good examples from analog and around in the net.
But If I were you I would use a cheap one and make my own dual or quad slope with a few 4051 mux in front of it as I remember you want to measure DC signals and mostly you design as cheap as possible for mass production


Or use a cheap 1-channel ADC and a HC4051. That's really hard to beat.

--
Regards, Joerg

http://www.analogconsultants.com
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