According to data sheet, the typical accuracy is 0.0017 C. Where does this
number come from? The repeatability number is a factor of ten higher.
Yes, this is a bit confusing. But note this is just a typical value, and we are
not saying ADT7420 is 0.0017 accurate, as it would probably make no sense. The
way how this is measured is as follows :
An oil bath is setup at 25C, the ADT7420 and a very accurate thermometer
(bigger resolution as well) are submerged into it. The temperature is recorded
for both devices, and the error will be the difference between the two values.
This was done across a certain number of parts, and finally the average error
was taken, hence this value could be smaller than the resolution. Some
measurements are positive, some of them are negative, and it ends up on an
average like the one shown.