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Melexis announced the introduction of a new current sensor chip, the MLX91235, which eliminates the magnetic core design and enables more accurate measurement of high currents flowing through the external main conductors such as PCB tracks and bus bars. Designed for automotive and alternative mobility, the product supports a wide range of applications such as inverters, battery management systems (BMS), and the low-voltage side of DC-DC converters.

Power electronics designers in the field of modern electric vehicles (EVs) have always faced the dual challenge of system size and weight, and the need for smaller and lighter solutions is urgent. Melexis's gradient measurement sensor MLX91235, by eliminating the core design of magnetic agglomeration, achieves a more compact size design than traditional current sensor technology and effectively eliminates measurement errors caused by hysteresis. The sensor utilizes differential magnetic field measurement technology between the two internal sensing elements, which not only provides highly accurate current feedback, but also effectively resists the influence of stray magnetic fields. With a bandwidth of 500kHz and a response time of just 2 microseconds, the MLX91235 also demonstrates excellent performance in high-speed applications such as motor control and converters.

Digital architecture and precision

With an intelligent digital architecture, the MLX91235 improves sensor performance while ensuring superior measurement accuracy and integrates several key functions to greatly improve the efficiency of development, calibration and system integration. Compared to piecework linear compensation methods commonly used in analog architectures, the digital architecture of the MLX91235 shows a greater ability to deal with inherent nonlinear properties, enabling more precise and advanced compensation strategies, resulting in more accurate and smooth data output. In addition, the sensor is equipped with fully digital temperature compensation technology, which further ensures high precision measurements across the entire operating range.

Open calibration via SPI

The MLX91235 has an "open" calibration design and is configured via a standard serial peripheral interface (SPI), enabling easy online calibration for any microcontroller unit (MCU). Compared with analog coreless sensors, the digital calibration method is more intuitive and fast, and parameters such as digital gain correction can be easily adjusted, which greatly improves the flexibility and efficiency of calibration.

Overcurrent detection and temperature monitoring

The MLX91235 has built-in 16-bit overcurrent detection (OCD), supports asymmetric threshold Settings, and offers two freely configurable threshold intervals. In addition, the feature has a configurable detection time of as little as 2 microseconds and the option to apply a false positive prevention policy to reduce false positives in environments with poor electromagnetic compatibility (EMC). The MLX91235 also incorporates a 10-bit temperature feedback mechanism, enabling precise output of junction temperature measurements with the help of a high-speed SPI interface.

Functional safety and self-test

The MLX91235 is ISO 26262 compliant and is certified as a Safe Element of an Independent Environment (SEooC) compliant with ASIL Level B. In addition to meeting the strict requirements of ASIL B, the sensor also has an advanced self-test function built in, which can be easily triggered via the SPI interface. This self-test enables comprehensive monitoring and reporting of key parameters including temperature, undervoltage, and mechanical stress. It is worth mentioning that compared with traditional diagnostic methods, this self-test function covers the complete signal chain from the sensor to the application MCU.

Bruno Boury, Product Line Director at Melexis, said: "Melexis has a long history in sensing technology, and the core-free sensor MLX91235 is the leader in our new generation of products," he further explained. "This sensor combines fast online calibration, OCD capabilities, ISO 26262 compliance and the high precision that comes with a digital core. These exceptional features, combined with the comprehensive support we provide to our customers, are key to Melexis' success in bringing this new technology to the field."

The MLX91235 is specifically designed for current sensing applications in the automotive and industrial sectors and is widely used for PCB and bus current sensing in inverters, low voltage DC-DC converters, chargers, electric heating catalysts (EHCs), battery management systems (BMS), intelligent thermal fuses and other systems.

Both the MLX91235 engineering sample and the DVK91235 development kit are available. The product is expected to be fully certified in mid-2025. If you want to know more, please visit http://www.melexis.com/MLX91235.

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