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Questions about AD7689

Question asked by Mr_M_from_G on Nov 19, 2014
Latest reply on Nov 20, 2014 by maithil

Hello,

I plan to use AD7689 and have some trouble to clearly understand the data
sheet.

My plan is to use 3 inputs as bipolar differential with their “ground” at the
level of Vref/2 either at the corresponding negativ input (eg. IN1, IN3, IN5)
or at COM, I did not decide about this yet (Any hints on advantages and
disadvantages are welcome) and two other inputs as unipolar single ended with
their ground at Gnd.

Can I do this from the electrical point of view or do I violate any specs?

How do I switch between channels and how long, how many conversions will it
take till I get the valid result?

Am I free to chosse input pins, which is differential and which single ended or are there rules to be followed?


update:

Just looked at EVAL-AD76MUXEDZ schematics and there is a filter or "charge reservoir" with 22 ohms and 2700pF in front of each analog input. I couldn't find anything about this in the data sheet. Do I need it or can I simply connect the analog inputs to an op amp output?

Thanks a lot for any help

Martin

 

Nachricht geändert durch Martin Mensch

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