Design of thermal sigma-delta modulators for smart thermal sensors

This paper describes a new class of A/D converters based on the so called thermal sigma-delta principle. This class of converters is closely related to the conventional electrical sigma-delta A/D converter. A considerable part of the conversion functions is, however, performed in the thermal signal domain, resulting in a small, highly flexible and accurate configuration for the read-out and A/D conversion of thermal sensor signals. Two smart thermal flow sensors incorporating the thermal sigma-delta technique have been realized in both bipolar and BiCMOS processes, showing the advantages of the thermal sigma-delta technique. An integrated smart sensor suited for high speed (response time <10 ms) respiration monitoring and control as well as a sensor with an I²C bus interface both using the thermal sigma-delta technique are presented