Coreless Current Sensor With 2μs Response Time

An innovative coreless current sensor offers precise, compact, and efficient solutions for modern automotive systems.

Researchers from Melexis, Belgium, have developed the ‘MLX91235’, an innovative current sensor, which eliminates the need for a ferromagnetic core. This breakthrough technology reduces sensor size while ensuring precision, especially in automotive and alternative mobility applications such as inverters, battery management systems (BMSs), and low-voltage DC-DC converters.

By discarding the ferromagnetic concentrator, the sensor achieves a smaller footprint and eliminates hysteresis-induced errors, a common limitation in traditional current sensors. The sensor’s gradiometric design measures magnetic fields with high accuracy, mitigating the effects of stray fields. With a 500kHz bandwidth and a swift 2μs response time, it is well-suited for high-speed applications like motor control and power converters.

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The sensor is aimed at designers and engineers working in automotive and industrial sectors, particularly those seeking compact, efficient solutions for power electronics. Its suitability for printed circuit boards (PCB) and busbar applications ensures its relevance in systems like smart pyro fuses, chargers, and electrically heated catalysts.

It leverages a digital architecture to enhance performance. Contrasting with conventional analog systems, its digital design enables advanced compensation for non-linearities, ensuring smooth and precise output. Additionally, a fully digital thermal compensation mechanism provides accurate measurements across diverse operating conditions.

Configuration is simplified through an open calibration interface using a standard serial peripheral interface (SPI). This digital calibration offers quick and direct adjustments, such as digital gain correction, compared to slower analog alternatives. It also incorporates robust safety and diagnostic features. It includes a 16-bit over-current detection (OCD) system with configurable thresholds and debounce strategies to minimise false positives in challenging electromagnetic environments. A 10-bit temperature monitoring mechanism transmits junction temperature data via SPI, enhancing system reliability.

Certified ISO 26262 compliant as an automotive safety integrity level (ASIL) B safety element out of context (SEoOC), it integrates a self-test feature triggered via SPI, enabling thorough diagnostics from the sensor to the application’s microcontroller unit.

“Melexis has a rich history in current sensing technologies and the coreless MLX91235 is our next step,” stated Bruno Boury, product line director, Melexis. He further adds “This sensor brings the optimal mix of in-situ fast calibration including OCD, ISO26262 compliance, and high accuracy owing to the digital core of the sensor. Those features combined with the Melexis customer support are a recipe for success in introducing this new technology into the field”

By addressing industry challenges with precision and efficiency, this sensor marks a significant leap in current sensing innovation.