Pressure Sensor ICs for Internal Combustion Engine and Hybrid Engine EVAP Systems

Recently, Melexis announced the MLX90821, a relative pressure sensor IC designed to measure very low pressures in automotive applications. It is reported that the MLX90821 adopts the latest MEMS technology and is a system-in-package solution in which a MEMS sensor and a CMOS signal processing chip are tightly integrated in the same package. It is suitable for measuring fuel vapor pressure as low as 50 mbar and as high as 700 mbar. Therefore, the MLX90821 is suitable for EVAP systems (fuel evaporation control systems) designed for internal combustion engines or hybrid vehicles.

  Pressure Sensor ICs for Internal Combustion Engine and Hybrid Engine EVAP Systems

Importance of EVAP System

Fuel pressure vapor detection using EVAP systems is now a necessity for automakers. There are two reasons for this:

1. The EVAP system captures, stores and treats fuel vapors, thereby preventing the vapors from escaping into the air and causing pollution. In recent years, more and more regions have introduced strict regulations prohibiting the emission of fuel vapors to the atmosphere, and it has become increasingly important for automakers to use EVAP systems for fuel pressure vapor detection.

2. It is an important way to improve the fuel-saving effect of automobiles, to ensure that the fuel is fully burned and not to lose fuel halfway. The EVAP system can collect fuel vapor, and send it into the intake manifold in a timely manner, and then enter the engine to burn after mixing with the normal mixture, so that the fuel can be fully utilized.

The utility of pressure sensor ICs

An EVAP system is integral, and pressure sensor ICs such as the MLX90821 that can measure very low pressures are a key component of such systems because they are able to detect very small leaks that can occur anywhere in the EVAP system. Of course, this is only possible if the measurement range, reliability, stability and accuracy of this category of products are sufficient for EVAP systems for internal combustion and hybrid engines.

According to Laurent Otte, pressure sensor product line manager at Melexis, the MLX90821 has such advantages over the pressure sensor, “With this sensor IC that is factory calibrated and can be custom calibrated for each individual application, Tier 1 and module manufacturers Capable of standardizing a single design for both engines. The sensor IC is packaged in a very reliable and easily hermetically sealed package and is certified to operate from -40°C to +150°C with full PPAP support .”

Specifically, the MLX90821 system-in-package solution uses a MEMS sensor fabricated by backside etching technology. As a result, the sensing element has high media compatibility against 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 a very high level of EMC protection and immunity, and can be easily designed for integration into EVAP systems for ICE and hybrid vehicles.

It is also understood that each sensor IC is calibrated in the final production step, storing the pressure transfer curve and clamping level in the internal EEPROM. Measurement results are provided via proportional analog output or SENT output, which can include temperature measurement. When the application also needs to output the accurate temperature measurement value 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.

It is worth mentioning that fuel vapor pressure measurement in HEVs is even more complex and requires more powerful sensing solutions. Also, since EVAP systems in ICE (internal combustion engine) and hybrid vehicles may have multiple pressure sensor ICs, it is critical to have a flexible and simple design.

The MLX90821 is small in size, can be used in almost any size module, and can be highly integrated through a system-in-package. It is a simple design, “plug and play” solution. The DSP provides analog output and SENT output, which can make full use of the fast and slow channels of the SENT interface to add diagnostic messages and customer-defined information. The MLX90821 provides a variety of diagnostic functions required in an automobile, including clamp levels, open circuit tracking diagnostics, and various internal fault diagnostics.

Market demand remains strong

Melexis provides advanced technologies for all pressure sensor fields, including signal conditioning ICs for high-voltage applications, packaged and factory-calibrated relative and absolute pressure sensor chips for low-voltage measurements, and more. These high-stability, high-performance plug-and-play solutions meet the harsh automotive environment requirements and are suitable for a variety of applications such as fuel vapor pressure, intake manifold absolute pressure (MAP), seat lumbar pressure, and motorcycle MAP pressure.

As mentioned earlier, MLX90821 is aimed at internal combustion engine vehicles or hybrid vehicles. In other words, the development of these two major market fields determines the application prospects of this scheme to a certain extent. As we all know, today’s increasingly stringent fuel consumption and emission regulations, as well as the industrial policy of fuel consumption limits and new energy “double points”, have accelerated the development of pure electric vehicles. Will this affect the development of the internal combustion engine vehicle or hybrid vehicle market? Woolen cloth?

The fact is that although pure electric vehicles can meet the fuel consumption with ease, it is undeniable that there are still many problems such as cost and battery technology that need to be solved. Therefore, for a long period of time, the diversified coexistence of pure electric vehicles, hybrid vehicles, pure fuel vehicles and other models is the general trend.


Laurent Otte, Product Line Manager for Melexis Pressure Sensors

Recently, Laurent Otte, product line manager (pressure sensor) of Melexis, a global microelectronics engineering company, also affirmed this. He pointed out that for a long period of time in the future, the automotive field will coexist with various forms of power, among which there will be a significant growth in hybrid vehicles. According to the relevant analysis and forecast of Gasgoo Automotive Research Institute, by 2025, nearly 90% of vehicles will still be equipped with internal combustion engines, among which hybrid vehicles will grow rapidly. After rising, this share will reach nearly 30% by 2025.

This means that product solutions such as the relative pressure sensor MLX90821 are still in great demand.

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