Melexis has announced a new sensor technology that promises to significantly advance electric vehicle thermal management systems. The microelectromechanical system (MEMS) sensor uses a patented design that delivers a more robust MEMS pressure sensor.
New Melexis pressure sensor for EV thermal management applications.
The MLX90830 chip is factory-calibrated to measure gas and liquid pressures from 2 to 70 bar. The ability to measure gaseous and liquid states and survive solid (frozen) states means that the sensor can operate under all conditions that an electric vehicle is likely to experience.
Thermal Management in Electric Vehicles
While electric vehicles (EVs) have fewer moving parts than internal combustion engine (ICE) vehicles, they still require cooling and heating and have critical thermal management requirements for the various systems. EVs use a heat pump system, essentially an air conditioner, to manage both the passenger compartment temperature and battery thermal condition. Air conditioning requires low-pressure sensing before the coolant compressor and high-pressure sensing after the compressor. The MLX90930 (datasheet linked) comes in two factory-calibrated pressure ranges (10 or 35 bar), allowing it to fulfill both roles.
Melexis’ Patented Triphibian Design
The device combines electronics and the sensor into a standard SO16-sized IC package. The patented sensing component is a piezo-resistive element configured as a Wheatstone bridge. The bridge output is amplified and sent through an analog-to-digital conversion stage. In the next step, a 16-bit digital signal processor (DSP) manages temperature compensation. Finally, the signal is converted back into an analog output. Delivering an analog output allows direct-replacement compatibility with standard existing sensors while delivering the advantages of a new MEMS device.
Cantilever design mitigates common MEMS weaknesses.
One of the unique design aspects of the MLX90830 is the cantilevered MEMS sensor element. This design allows for spike pressure up to 2,000 bar/msec and continuous overpressure static burst pressure to 210 bar. More conventional MEMS devices can suffer from weakness in the standard construction, leading to much lower overpressure limits.
Conventional MEMS compared to Melexis MLX90830.
When a conventional MEMS sensor is used in a bottom-side exposed scenario, as shown in the image above (left), overpressure can break the glue bonds and dislodge the sensor element. With a top-exposed construction, the conventional sensor element is subject to crushing or fracturing. The cantilever construction in the Melexis Triphibian architecture mitigates both of those potential risks. It even allows the device to survive the sensing medium freezing over.
New Technology in a Compatible Package
The SO16 package is architected so that the chip can fit within the industry-standard pressure sensor housing. With that configuration, the sensor can be used as a direct replacement for conventional ceramic (non-MEMS) pressure sensors or for other MEMS sensors.
Melexis Triphibian sensor in standard product form factor.
The part boasts configurable diagnostics, a +/- 0.5% full-scale lifetime accuracy, response times of 0.4 ms, +40 V and -40V overvoltage capability, and an automotive temperature range of -40°C to 150°C. It meets AEC-Q100 and AEC-Q103-002 certification and is ASIL compliant, developed as an ISO 26262/ASIL A SEooC device.
All images (modified) used courtesy of Melexis.