Brad:
I don't work for that company any more, so I don't know if they ever got a solution. I know that my generic TI login which follows me from job to job did not receive a solution.
I never got a satisfactory response from TI. The problem is that this is an old National Instruments part that appears to have been designed by an engineering student doing his master's work. I was extremely disappointed with the quality of the documentation and the operation of the part. TI is a very good company with a lot of good products; just not this one.
We ran into problems with weird things happening if you push the part into "saturation" by using too much bias current into the reference resistor. That was pilot error and not due to the TI part, but I don't recall if we had other issues that got solved.
I noticed some *very* odd behavior with the reference design. We set it up with a thermistor using the app note. When I would run a sequence of readings, the A/D value would start high and drift down perhaps 20% with an exponential response. Obviously, that is unacceptable.
My recommendation is to design in another TI part. I rate it a zero on a scale of 1 to 10.
Ray