I have a general question regarding the accuracy of voltage references as they pertain to ADCs. Specifically, I was under the impression that the accuracy of the reference was a key component in providing accurate and consistent ADC results.
But, a specification for a analog front end from MCP, the MCP3911
has me a bit confused. On the one hand, MCP claims that the MCP3910 can be used for power measurements that exceed 0.1% in accuracy and that the references that are built into these chips have very low drift (<10PPM/*C) but the actual accuracy of the reference is about +/- 2%.
Is the explanation that while the reference is "only" 2% accurate, it is very stable in terms of its output? It certainly seems very stable re: ambient temperature, for example. Thus, the error of the reference is so consistent that it can be calibrated out of existence?