PCB-less pressure sensor IC platform has extended robustness to harsh media

Melexis has added two new products to its PCB-less pressure sensors family. The MLX90823 (analogue output) and MLX90825 (digital SENT output) are relative pressure sensors which may be utilised in gauge mode (versus the atmospheric pressure) or a differential mode (with two variable pressure levels). Unlike absolute pressure sensors, they calculate the pressure difference between the two sides of the sensor. These factory-calibrated devices are aimed at measuring pressure spanning from 0.1 to 1.5 bar.

The sensors display an accuracy performance yet to be encountered in the automotive industry. Access to stable and accurate data on pressure and temperature allows complete lifetime engine management, which helps OEMs reduce emissions on the last generation of ICE cars. The plug-and-play concept of this pressure sensor family includes all the ICE management applications. These include fuel vapour and crankcase ventilation, EGR, GPF/DPF, secondary Air Injection, and (T)MAP.

Laurent Otte, senior product line manager at Melexis, said: “With a complete portfolio of PCB-less products, customers and OEMs can address each pressure application. Customers benefit from a platform approach with high reusability, which reduces development costs and accelerates time to market.”

The devices comprise a sensor readout circuit, digital hardware, voltage regulators, SENT or analogue output drivers, and all the essential passive components. A pre-calibrated (NTC) thermistor input is provided for the MLX90825 (SENT output). This enables customers to interface their NTC via the pressure sensor without end-calibration. Superior overvoltage (+40V) and reverse voltage (-40V) protection mechanisms are included. Thanks to this protection range, the technology allows trucks to become greener. These pressure sensors have an operating temperature range from -40C to 160C. They can even be exposed to 170C temperatures for a short period, supporting downsized engine architectures.

The MEMS sensing element of the devices comprises a micro-machined diaphragm etched into a silicon substrate. The diaphragm responds to any pressure change that ensues. Piezo-resistive elements implanted into the diaphragm are configured to produce a Wheatstone bridge that generates a signal. The accompanying front-end electronics thereafter amplify the signal and convert it into a digital format. The 16-bit DSP undertakes temperature compensation. Finally, the result is delivered through a SENT or analogue output.

The devices have been developed as a SEooC in accordance with ISO 26262. They support ASIL B system integration for the MLX90825 (SENT) and ASIL A for the MLX90823 (analogue).

“Having access to a family of PCB-less sensors that also covers differential modes creates new opportunities for our customers,” stated Karel Claesen, product manager pressure sensors, Melexis. ”The customers benefit from this unique modular technology to cover demanding applications such as diesel and gasoline particulate filters.”