> Thanks Micheal,
>
> that should help in the future.
>
> Could you address my main issue here? Is it realistic to try to get
> 12 bit accuracy off these boards (within the limits stated in the
> MAX197 datasheet) or are we expecting too much?
>
> I'm quite willing to believe this noise may be coming from the
> external cct but don't want to spends days/weeks fault finding only
> to discover that I am trying to achieve the impossible.
>
> To be clear , I'm not refering to absolute accuracy here. Just
> whether it is possible to get a clean reading +/- 1 LSB while
> sampling just one channel.
>
> I need to make a decision very soon now on whether these boards are
> able to fullfil our spec requirements.
>
> Thanks for any information your engineers can provide.
Here is the story on the MAX197 on the TS-7250. The chip has it's own power
and ground, by virtue of the fact that they are isolated from the rest of
the power and ground planes of the board. There is a resistor/cap on the
incoming power as recommended by the datasheet, and only a single point of
shared ground with the rest of the board (which of course it has to have).
We expect that +/- 1 LSB is possible, but we have never done any detailed
analysis on the board to determine whether or not this is true.
As a previous poster mentioned, it would be very simple to turn off the
Ethernet chip and see if the periodic 6mV noise you are seeing goes away.
If that is the problem we definitely would be interested in having that
information for future reference.
> best regard,
>
> jacques.
______ Best Regards,
|__ __/ Michael Schmidt
|| Software Engineer
||echnologic Systems (EmbeddedARM.com)
|| (480) 16610 East Laser Drive #10
|/ 837-5200 Fountain Hills, AZ 85268
http://oz.embeddedarm.com/~michael
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