Unique relative pressure sensor ics for ICE and EVAP systems for hybrid vehicles

     Melexis has announced the introduction of the relative pressure sensor IC MLX90821, designed to measure extremely low pressures in automotive applications. Using the latest MEMS technology, the MLX90821 is a system-level package solution tightly integrated with analog signal chain and digital signal processing technology in the same package for measuring fuel vapor pressures from as low as 50 mbar to as high as 700 mbar. Therefore, the MLX90821 is suitable for EVAP systems designed for internal combustion engines or hybrid electric vehicles.

     With more and more regions introducing stringent regulations that prohibit the discharge of fuel vapor into the atmosphere, it is becoming increasingly important for vehicle manufacturers to use EVAP (evaporation) systems for fuel pressure vapor detection. Steam builds up in the fuel tank and crankcase, and the EVAP system captures, stores and processes it to prevent it from escaping into the air. Pressure sensor ics that can measure extremely low pressures, such as the MLX90821, are a key component of this class of systems because they are able to detect extremely small leaks that may occur anywhere in the EVAP system.

     "The measurement range, reliability, stability and accuracy of the relative pressure sensor MLX90821 are sufficient for EVAP systems for internal combustion and hybrid engines." Laurent Otte, product line manager for pressure sensors at Melexis, commented. "With this factory-calibrated sensor IC that can be custom calibrated for each individual application, Tier 1 and module manufacturers are able to adopt a standardized single design for both engines. The sensor IC is packaged in a reliable and easily sealable package and is certified to operate in the temperature range from -40°C to +150°C, with full PPAP support."

     Fuel vapor pressure measurement for hybrid vehicles is even more complex and requires more powerful sensing solutions. In addition, because EVAP systems in ICE (internal combustion engine) and hybrid vehicles may be equipped with multiple pressure sensor ics, a flexible and simple design is critical. The MLX90821's compact size allows it to be used in virtually any size module and offers a high degree of integration in a system-level package, making it a simple, "plug and play" solution. The DSP provides analog output and SENT output, and can make full use of the fast or slow channel of the SENT interface to add diagnostic messages and user-defined information. The MLX90821 provides a wide range of diagnostic functions required by the vehicle, including clamp levels, open circuit tracking diagnostics, and multiple internal fault diagnostics.

     The system-level package solution uses MEMS sensors manufactured by backside etching technology. As a result, the sensing element has high dielectric compatibility against contaminants when exposed to harsh environments such as fuel vapors or other media. The CMOS component of the system provides design flexibility, while the entire sensor provides extremely high levels of EMC protection and immunity, and can be simply designed to be integrated into the EVAP systems of ICE and hybrid vehicles.

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