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Automotive pressure sensor makes combustion engines greener

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By Christoph Hammerschmidt


Melexis has launched a range of PCB-less pressure sensor ICs that, according to the manufacturer, offer the highest level of lifetime accuracy. This performance will make Internal Combustion Engines (ICEs) more environmentally friendly.

Melexis’ new pressure sensors are intended for use in automotive engine management. The MLX90824 determines the absolute pressure, then delivers a digital output signal using the SENT protocol whereas the brother product MLX90822 provides an analog output voltage. These factory calibrated devices measures pressure spans from 1 to 4 bar.

According to Melexis, 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, the company says. 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 analog 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: As part of the motor management, accurate pressure data positively influence fuel saving and emission reductions.

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 analog 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.

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 3 times faster than any other pressure sensor ever made by Melexis.

The MLX90824 and MLX90822 help OEMs with their battle to reduce emissions and. They make sure that cars, trucks and motorcycles will be compliant with the latest emission standard.

https://www.melexis.com


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