Integrated MEMs sensors

Melexis' MLX90807 and MLX90808 fully integrated, relative and absolute pressure sensor die are have been realised with cmos technology combined with MEMS bulk micromachining.

The monolithic solutions are both fully automotive qualified. Each consists of a silicon membrane with piezoresistors to transform the stress induced by pressure into an electrical signal. An analogue signal chain interacting with a digital core, including programmable memory, allows full calibration on chip in order to achieve an optimised transfer function over the desired working pressure and temperature range. The Melexis integrated pressure sensor die cover many pressure ranges from a span of 100mbar to several bars. Their use is straightforward when the media to be measured is relatively benign like dry air found in barometric sensing or engine intake manifolds, brake boosters or even stronger media like fuel vapour. For harsher media applications like oils, liquids and engine exhaust gas, the Melexis chips must include special, secondary protection for the die. The pressure sensors are fully programmable through the connector with built in protection against all typical overvoltage automotive conditions. The devices include circuitry that meets all automotive diagnostic requirements including broken membrane detection and short and open circuit conditions. Melexis' product marketing manager, Laurent Otte says: "Experimental data from stress testing shows the MLX 90807 and 90808 are capable of having the MEMs diaphragm cycled many times in excess of the standard test limits without failures."