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Melexis Introduces Relative Pressure Sensor ICs for Measuring Extremely Low Pressures in Automotive Applications

On November 1, 2019, Tysondro, Belgium – Global Microelectronics Engineering Company Melexis announced the introduction of the MLX90821, a relative pressure sensor designed to measure extremely low pressures in automotive applications.

The automotive-compliant MLX90821 measures relative pressures as low as 50 mbar. Using the latest MEMS technology, the MLX90821 is a system-in-package solution that is tightly integrated into the same package with analog signal chain and digital signal processing technology for measuring fuel vapor pressures as low as 50 mbar up to 700 mbar. Therefore, the MLX90821 is suitable for EVAP systems designed for internal combustion engines or hybrid vehicles.

As more and more regions introduce strict regulations prohibiting the release of fuel vapors into the atmosphere, it is increasingly important for automakers to use EVAP (evaporation) systems for fuel pressure steam detection. Steam builds up in the fuel tank and crankcase, and the EVAP system captures, stores, and processes steam to prevent steam from escaping into the air. Pressure sensor ICs that can measure extremely low pressures (such as the MLX90821) are a key component of such systems because they detect very small leaks that can occur anywhere in the EVAP system.

“The relative pressure sensor MLX90821’s measurement range, reliability, stability and accuracy are sufficient for EVAP systems for internal combustion engines and hybrid engines,” commented Laurent Otte, product line manager for Melexis pressure sensors. “With this factory-calibrated sensor IC that can be custom calibrated for each individual application, Tier 1 manufacturers and module manufacturers can use a standardized single design for both engines. The sensor IC package is reliable and easy to use. Sealed and certified for operation from -40°C to +150°C with full PPAP support.”

Hybrid vehicles’ fuel vapor pressure measurements are even more complex and require more powerful sensing solutions. In addition, since the EVAP system in ICE (internal combustion engine) and hybrid vehicles may be equipped with multiple pressure sensor ICs, it is important to adopt a flexible and simple design. The MLX90821 is a compact, “plug and play” solution that can be used in almost any size module and is highly integrated in a system-in-package. The DSP provides analog output and SENT output to take advantage of the fast and slow channels of the SENT interface, adding diagnostic messages and customer-defined information. The MLX90821 provides a variety of diagnostic functions required for automotive applications, including clamp levels, open circuit trace diagnostics, and a variety of internal troubleshooting.

The system-in-package solution uses MEMS sensors fabricated by backside etching. As a result, sensing elements have high media compatibility for contaminants when exposed to harsh environments such as fuel vapors or other media. The CMOS portion of the system provides design flexibility, and the entire sensor provides an extremely high level of EMC protection and immunity, and is easily integrated into EVAP systems for ICE and hybrid vehicles.

Each sensor IC is calibrated during the final production step, storing the pressure transfer curve and clamp level in the internal EEPROM. The measurement results are provided by a proportional analog output or SENT output and can include temperature measurements. When the application also needs to output the accurate temperature measurement value of the measured medium, you can choose to use the external NTC and output the temperature value after temperature compensation. Further configuration can be done using hardware and software tools provided and supported by Melexis.

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