The new current sensor eliminates the need for a ferromagnetic core

     Melexis has introduced the MLX91235, a new type of current sensor that eliminates the need for a ferromagnetic core. Designed to meet the needs of automotive and industrial current sensing applications, the MLX91235 supports PCB and bus current sensing in systems such as inverters, low voltage DC-DC converters, chargers, EHCs, bms, intelligent thermal fuses, and more. The device expands its portfolio to allow greater current to be measured through external primary conductors, such as PCB wiring and bus bars. It supports automotive and alternative mobile applications such as inverters, bms and low-voltage DC-DC converters.

     Power electronics designers are constantly faced with the challenges of the size and weight of modern electric vehicle systems, resulting in an ongoing need for smaller, lighter solutions. By eliminating the ferromagnetic concentrator, the footprint of the gradient measuring device is significantly smaller than that of current typical sensor technology and the measurement error associated with hysteresis is eliminated. Differential magnetic field measurement between the two internal sensing elements provides accurate current feedback and eliminates stray field effects. With a 500kHz bandwidth and a 2μs response time, the sensor is ideal for high-speed applications, such as motor control and converter applications.

     The device's intelligent digital architecture elevates the sensor offering, ensures high measurement accuracy, and combines several key features to help improve development, calibration, and system integration. When dealing with inherent nonlinearity, simulation architectures often rely on piecewise linear compensation. However, the device's digital architecture allows for more precise and complex compensation, resulting in a more accurate and smoother output. The all-digital based thermal compensation further ensures that it provides the highest precision measurements under its operating conditions.

     The device's "open" calibration is configured via standard SPI, allowing for field configuration via any MCU. Digital calibration provides a more direct and faster experience than analog coreless sensors, allowing for easy adjustments to elements such as digital gain correction.

     The built-in 16-bit overcurrent detection (OCD) allows for asymmetric thresholds and includes two configurable threshold ranges. It provides a configurable detection time with a minimum duration of 2μs and an optional stripping strategy. This strategy helps avoid false positives in harsher EMC environments. Further enhancing its value, the MLX91235 also includes a 10-bit temperature feedback mechanism that enables accurate junction temperature measurement via high-speed SPI output transmission.

     The device complies with ISO 26262 as an ASIL B Safe Element out of Context (SEoOC). In addition to ASIL B requirements, it also integrates a sophisticated built-in self-check function that can be triggered by SPI. This feature enables the sensor to report critical information such as temperature, undervoltage, and mechanical stress. Notably, unlike traditional diagnostics, this feature includes a complete signal chain up to the application MCU that reads the sensor.

     "Melexis has a rich history in current sensing technologies and the cordless MLX91235 is our next step," said Bruno Boury, Melexis Product Line Director. He continued, "The sensor brings the best combination of in situ rapid calibration, including OCD, compliance with the ISO26262 standard, and high precision thanks to the sensor's digital core. These capabilities, combined with Melexis' customer support, are the recipe for a successful introduction of this new technology into the space."