Melexis adds two new products to its family of PCB-less pressure sensors. The MLX90823 (analogue output) and MLX90825 (digital SENT output) are relative pressure sensors which can be used in gauge mode (versus the atmospheric pressure) or in a 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 intended to measure pressure spanning from 0.1 to 1.5 bar.
Access to stable and accurate data on pressure and temperature enables full lifetime engine management. This helps OEMs to reduce emissions on the last generation of ICE cars. The plug-and-play concept of this Melexis pressure sensor family covers all the ICE management applications. These include:
- Fuel vapour and crankcase ventilation: To ensure that fuel vapours in the tank or gasses leaking through pistons are brought back into the combustion chamber, preventing them from being released into the atmosphere.
- EGR, GPF/DPF: To reduce NOx emissions by sensing the amount of recirculated exhaust gasses in the engine intake and trapping the residual particulates in the exhaust filter.
- Secondary Air Injection (SAI): For keeping vehicles within the emission limits under all circumstances, including when the engine is cold. It enables a fast warmup of the catalytic converter with the so-called secondary air injection.
- (T)MAP: To monitor the air going into the engine for accurately regulating the fuel, thus reducing the consumption.
The MLX90823 and MLX90825 each consist of a sensor readout circuit, digital hardware, voltage regulators, SENT or analogue output drivers, plus all the essential passive components. A pre-calibrated (Negative Temperature Coefficient (NTC) thermistor input is available for the MLX90825 (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, the technology enables trucks to become greener. These pressure sensors have an operating temperature range from -40°C to 160°C. They can even be exposed to 170°C temperatures for a short period, supporting downsized engine architectures.
The MEMS sensing element of the MLX90823 and MLX90825 consists of a micro-machined diaphragm etched into a silicon substrate. The diaphragm reacts to any pressure change that occurs. 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 MLX90823 and MLX90825 have been developed as a Safety Element out of Context (SEooC), in accordance with ISO 26262. They support ASIL B system integration for the MLX90825 (SENT) and ASIL A for the MLX90823 (analogue).
