An integrated mass flow sensor with on-chip CMOS interface circuitry

A multielement monolithic mass flow sensor which developed for possible use in automotive and industrial process control applications is reported. The chip illustrates the use of a common microstructure (a thin dielectric window/diaphragm) for the simultaneous measurement of flow velocity (rate), flow direction, gas type, and pressure. These transducers are merged with on-chip interface electronics to amplify and multiplex the transducer signals, control on-chip actuators, perform self-test, reduce the number of external leads required, and demonstrate process compatibility with a p-well CMOS process. The on-chip circuitry also implements a bandgap sensor for the measurement of ambient temperature. Thus, the chip simultaneously monitors all parameters needed for the computation of true mass flow, requires only ten external leads, and delivers high-level buffered output signals