I am designing a high accuracy temperature sensor on 130nm CMOS process. Supply voltage is about 1.5v.
Sensor need to be within +/- 2 degree accuracy, from 0 ~ 125 degree.
My difficulty is that bandgap voltage reference itself is very hard to be controlled within 3%. How can we measure temperature by so coarse ruler?
Basically one needs to measure delta-Vbe voltage with high accuracy.
To do it use a switched-cap auto-zeroed amplifier.
To get an accurate bandgap reference to compare with, use a similar auto-zeroed amplifier in the reference loop. Some sort of curvature correction should be added also. All this combiled should give you the necessary accuracy.
Good luck!