Control and detection circuitry for mass airflow sensors

摘要

A mass airflow sensor is disclosed which uses a small, thin dielectric diaphragm providing good thermal isolation for thin-film heating and temperature sensing elements, resulting in high flow sensitivity and low current operation of the heating element. The dielectric diaphragm is bounded by a p-etch-stopped silicon rim. The mass airflow sensor includes a primary sensor circuit which maintains a heated primary temperature sensing element and an ambient air temperature sensing element at a constant temperature difference. A slave sensor circuit, which includes a plurality temperature sensing elements, monitors heat loss due to airflow at a particular location on the diaphragm and generates an output signal indicative of airflow which is independent of ambient air temperature.