MLX90821- MEMS Pressure Sensor for Evaporation Systems in ICE and Hybrid Vehicles


ByDinesh Kumar 0

MLX90821- MEMS Pressure Sensor for Evaporation Systems in ICE and Hybrid Vehicles

Melexis announced the MLX90821 relative pressure sensor IC designed for measuring low pressure (50mbar and up to 700mbar), which is ideal for EVAP systems designed for internal combustion engines or hybrid vehicles. The MLX90821 is a system-in-package IC solution that uses the latest MEMS technology closely integrated with an analog signal chain and digital signal processing.


The adaption of fuel pressure vapor detection using the EVAP (Evaporation) Systems is increasing as it is getting mandatory in many regions that have introduced strict legislation which prohibits the venting of fuel vapor to the atmosphere. As the vapor builds up inside fuel tanks and crankcases, the EVAP systems are designed to capture, store and responsibly dispose of the vapor, preventing it from escaping into the air. The pressure sensors like MLX90821 are crucial parts of the system as they can operate at very low pressure and detect even the smallest leaks that can appear at any point in the EVAP system.

Features and Benefits of MLX90821

  • High accuracy relative pressure sensor with a ratiometric analog output or digital SENT output, including compensated ±1 °C accurate NTC media temperature information.
  • Large automotive temperature range (-40 °C to 150 °C).
  • Automotive qualified and automotive diagnostic features (clamping levels, broken track diagnostics, multiple internal fault diagnostics)
  • Factory calibrated or fully programmable or reconfigurable through the connector for customized calibration curves at customers
  • Backside exposed relative pressure sensor for higher resistance to common automotive media
  • Assembled into a robust and easy-to-seal package


The fuel vapor pressure sensing is more complex in hybrid vehicles hence there is a demand for more capable sensing solutions. Designing with the MLX90821 is easy due to its small size and high level of integration provided through the system in package approach which provides a plug & play approach. While both analog and SENT outputs are provided, the DSP offers the ability to make full use of the SENT interface’s fast channel and slow channel, add diagnostic messaging and apply custom calibration.


The system-in-package approach uses a MEMS sensor manufactured by backside etching which allows the sensing element to be exposed directly to the vapor or other media along with the robust protection against contaminants present in the harsh environment such as fuel vapor systems. The CMOS part of the system provides flexibility and the entire sensor offers exceptionally high levels of EMC protection and immunity, making it simple to design into EVAP systems for both IEC and hybrid vehicles.


Each sensor IC is calibrated during the final steps of manufacture, with the pressure transfer curve and clamping levels stored in the internal EEPROM. The measurement is provided through the ratio metric analog output or as a SENT output, which may also contain temperature measurements. An optional NTC temperature compensation feature makes use of an external NTC, which may be required when the application also needs to record an accurate temperature measurement of the media being monitored. Further configuration is possible using software tools provided and supported by Melexis. For more details about the MLX90821 and to download the datasheet visit the product page on the official website of Melexis. 

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