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AD7730 ACX and !ACX signals referenced to AGND and NOT DGND

Question asked by sborden on Apr 26, 2013
Latest reply on Apr 26, 2013 by MaryMc

Is this a correct observation?  I am trying to implement AC-excited  +5/-5 load cell.  I reduced the AVDD and AGND using op-amps as suggested, then run +5/-5 to the load cell through analog switches.  The reference voltage comes back to the AD7730 split with the same resistor combination used for AVDD/AGND (0.1% precision, just to be sure).

 

I  made a mistake in the schematic in that the connection of the ACX/!ACX lines went to an unconnected pin of the analog switches, and that was for the good.  I was flabbergasted not to see 0V/5V on these lines, but instead  -2.5V and +2.5V.  This would have blown the switches.

 

Is something else wrong or are the ACX/!ACX lines actually referenced to AGND and NOT DGND as implied by the data sheet?

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