BICMOS INTEGRATED-CIRCUIT FOR CAPACITIVE PRESSURE SENSORS IN AUTOMOTIVE APPLICATIONS

A new integrated electronic circuit has been designed in cooperation w ith the most important French automotive industrial group which is wor king on the Prometheus programme. This circuit is connected to a diffe rential capacitive pressure sensor which varies from 30 to 40 pF when pressure increases from 0 to 5 bars. Resolution must be better than 0. 1 pF within the operating temperature range of -25-degrees-C- + 85-deg rees-C. The circuit uses a BiCMOS, an analog/digital mixed semicustom technology in order to give the best performance with a very low power consumption (250 muA) under a 5 V supply voltage. It consists of two main blocks: (i) the analog block with two triangular oscillators, and (ii) the digital block which gives an 11 bits-number proportional to the pressure, and is able to give failure diagnosis and to manage the power supply of the circuit. The design and the simulation have been d one and the electronic chip has been available since autumn 1992.