For measuring voltages, I have setup four channels that I will elaborate on below.
|Channel #||+ Input||- Input|
Before I setup the VBIAS register, floating inputs tended to cause very noticeable fluctuations in the internal temp sensor and the voltage readings. I have tried setting VBIAS on all inputs except the channel I want to read from, setting VBIAS on all the positive inputs (AIN5, AIN3, AIN2, AIN1), and setting VBIAS on all the negative inputs (AINCOM, AIN4). Right now, it seems that setting VBIAS on all negative inputs tends to perform the best. I can tell that VBIAS is set up properly if the voltages I am reading don't change if I connect other inputs or disconnect other inputs. I'm not sure if there is a correct way to set up the VBIAS register according to the inputs you intend to utilize. All I can really find on the data sheet about unused inputs is on the bottom of page 31 where it says not to overdrive an unselected input. Even though my query is pretty specific, I would appreciate any answer on dealing with floating or unused inputs and making sure they don't interfere with conversions.