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AD7746- which EXC signal to use

Question asked by keymoto on Mar 29, 2018
Latest reply on May 3, 2018 by keymoto

I'm using both CIN1+ and CIN2+ inputs on the AD7746 to read a columns on a large sensor grid. We would like to use both inputs in order to minimize the time spent waiting for signals to settle after changing which column is attached to the CIN1+ or CIN2+ input. 


The datasheet suggests that when using both inputs, both EXCA and EXCB should be used, but in order to cover the entire grid, we would either need to tie the two together to allow each row to have either EXCA or EXCB attached... or we would have to use EXCA only for both CIN1+ and CIN2+. 


What is the output stage like for the EXCA/B outputs? Are they open-drain, and therefore safe to tie together? 


Would it be better to use EXCA for both inputs? Why is it suggested to use both excitations when using both capacitive inputs?