I am having an issue with the ADC results that I am getting. Here is what I have. I am using an uPSD3454DV-40T6. I have 3 analog input that I am using on ADC5, 6, and 7. On ADC5 I have a 10K thermister. On ADC6 I have a 32.89K resistor and on ADC7 I have a 995 ohm resistor. I made a spreadsheet to caclulate the voltage at different resistances based off the data seet for the 10K thermister that I am using. I am using the resistors on ADC6/7 to verify the thermister curve for my lookup table.

On ADC5 I am able to calculate the voltage based on the counts I am getting from the ADC. My measured voltage matches up with my calculated result. On ADC6/7 The actual measured voltage is different than the calculated voltage based off the the counts that I am getting from the ADC. ex On the 995 ohm input I am getting 115 counts, and the measured voltage across the resistor is 301 mV. My calculated voltage is 373 mV and 1.266K resistance. I have calculated the expected counts at 301 mV to be 93. I have measured the voltage on ADC6 right at the pin to the input on the chip and it reads 301 mV.

Also, I have measured my Vcc to be 3.322 V.

Can anyone point me to where/why my result is not matching up with the inputed voltage? Why is it working fine on ADC5, and not on ADC6/7?

Let me know if more info is needed.

Thanks for the help,

Matt Barlage