With these pressure sensors, customers and original equipment manufacturers (OEMs) can make all their internal combustion engine (ICE) management applications more environmentally friendly using a unique modular technology. To further simplify implementation, the devices are factory calibrated, although periodic recalibration by the customer is also possible.

Melexis, a global microelectronics engineering company, has added two new products to its family of PCB-free pressure sensors. The MLX90823 (analog-to-analog output) and the MLX90825 (digital SENT output) are gauge pressure sensors that can be used in gauge mode (against atmospheric pressure) or differential mode (with two variable pressure levels). Unlike absolute pressure sensors, they measure the pressure difference between the two sides of the sensor. These factory-calibrated devices are designed to measure pressure variations between 0.1 and 1.5 bar.

The new pressure sensors offer unprecedented levels of accuracy in the automotive industry. Access to stable and precise pressure and temperature data enables comprehensive engine management throughout its entire lifespan. This helps original equipment manufacturers (OEMs) reduce emissions from the latest generation of internal combustion engine vehicles. The plug-and-play design of this Melexis pressure sensor family covers all internal combustion engine management applications, including:

● Fuel vapor and crankcase ventilation: To ensure that fuel vapors in the tank or gases that pass through the pistons are returned to the combustion chamber, preventing their release into the atmosphere.
● EGR, GPF/DPF: To reduce NOx emissions by detecting the amount of exhaust gas recirculated into the engine intake and trapping residual particles in the exhaust filter.
● Secondary Air Injection (SAI): To keep vehicles within emissions limits under all circumstances, even when the engine is cold. It allows for rapid warm-up of the catalytic converter through secondary air injection.
● (T)MAP: Monitors the air entering the engine to precisely regulate fuel delivery, thus reducing consumption.

Laurent Otte, Senior Product Line Manager at Melexis, states, "With a complete portfolio of PCB-free products, customers and OEMs can address every pressure application. Customers benefit from a platform approach with high reusability, which reduces development costs and accelerates time to market."

The MLX90823 and MLX90825 each consist of a sensor readout circuit, digital hardware, voltage regulators, SENT or analog-to-analog output drivers, and all essential passive components. The MLX90825 features a pre-calibrated thermistor input (SENT output) with a negative temperature coefficient (NTC). This allows customers to interface their NTC through the pressure sensor without final calibration. It incorporates superior overvoltage (+40 V) and reverse voltage (-40 V) protection mechanisms. This protection range enables the technology to make trucks more environmentally friendly. These pressure sensors have an operating temperature range of -40°C to 160°C. They can even withstand temperatures of 170°C for short periods, allowing for smaller engine architectures.

The MEMS sensing element in the MLX90823 and MLX90825 consists of a micromachined membrane etched onto a silicon substrate. The membrane reacts to any pressure changes. Piezoresistive elements embedded in the membrane are configured to create a Wheatstone bridge, generating a signal. The front-end electronics then amplify the signal and convert it to digital format. A 16-bit digital signal processing (DSP) unit compensates for temperature. Finally, the output is provided via a SENT or analog-to-analog signal.

The MLX90823 and MLX90825 have been developed as out-of-context safety elements (SEooC), in accordance with ISO 26262. They support the integration of ASIL B systems for the MLX90825 (SENT) and ASIL A systems for the MLX90823 (analog-to-analog).

“Having access to a PCB-free sensor family that also covers differential modes creates new opportunities for our customers,” said Karel Claesen, Product Manager for Pressure Sensors at Melexis. “Customers benefit from this unique modular technology to cover demanding applications such as diesel and gasoline particulate filters.”.