Melexis unveils accurate automotive pressure sensor

The MLX90824 determines the absolute pressure, then delivers a digital output signal using the SENT protocol whereas the brother product MLX90822 provides an analogue output voltage. These factory calibrated devices measures pressure spans from 1 to 4 bar.

Laurent Otte, Senior Product Line Manager, explains why these sensors help Melexis customers: “An accuracy of +/-0.5 %FS (full scale) is maintained over the course of the sensor’s working lifespan. This accuracy is not impacted by the sensor integration thanks to the PCB-less packaging.”

 Very accurate and stable pressure measurements allow optimal engine management to guarantee fuel savings and emission reductions.

The MLX90824 and MLX90822 consist of a sensor readout circuit, digital hardware, voltage regulators and SENT or analogue output drivers, plus all the essential passive components. A pre-calibrated NTC thermistor (negative temperature coefficient) input is available for the MLX90824 (SENT output). This allows customers to interface their NTC through the pressure sensor without end-calibration. Superior overvoltage (+40 V) and reverse voltage (-40 V) protection mechanisms are incorporated. Thanks to this protection range, trucks benefit from this technology to get greener. These pressure sensors have an operating temperature range that spans from -40°C to 160°C. They can even be exposed to 170°C temperatures for a short period of time, supporting downsized engine architectures.

The MEMS, sensing element of the MLX90824 and MLX90822, consists of a micro-machined diaphragm. It is bonded around a cavity that has been etched into a silicon substrate. This cavity contains a reference vacuum. The diaphragm reacts to any change in the ambient absolute pressure. Piezo-resistive elements implanted into the diaphragm are configured to create a Wheatstone bridge that generates a signal. The accompanying front-end electronics subsequently amplify the signal and convert it into a digital format. The 16-bit Digital Signal Processing (DSP) undertakes temperature compensation. Finally, the result is provided through a SENT or analogue output.

The MLX90824 and MLX90822 have been developed as a Safety Element out of Context (SEooC) in accordance with ISO 26262. It supports ASIL B system integration for the MLX90824 and ASIL A for the MLX90822.

“Access to stable and accurate data on pressure as well as temperature enable long-term engine management across the full lifetime of vehicles. This positively influences fuel saving and emission reductions,” states Karel Claesen, Product Manager Pressure Sensors. “The MLX90824 and MLX90822 are optimised for the latest engine designs and their new operating conditions.”

Last but not least for motorcycles or any equipment running on small engines such as chainsaws, lawn mowers among others it is essential to have a sensor with a very fast update rate and step response. The MLX90822 addresses that need with an output step response three times faster than any other pressure sensor made by Melexis.

The MLX90824 and MLX90822 help OEMs with their constant battle to reduce emissions and counters high fuel prices by lowering fuel consumption. They make sure that cars, trucks, and motorcycles will be compliant with the latest emission standard.