Melexis Shrinks Current Sensing Footprint With Coreless Technology

21.11.2024

Tessenderlo, Belgium, 21 November 2024 – Melexis unveils the
MLX91235,
a new current sensor that eliminates the need for a ferromagnetic core. The MLX91235
expands Melexis’ portfolio, enabling the measurement of larger currents flowing
through external primary conductors like PCB traces and busbars. It supports
automotive and alternative mobility applications like inverters, battery management
systems (BMSs) and low-voltage DC-DC converters.

Power electronic designers are constantly faced with the challenge of
system size and weight in modern electric vehicles (EVs), resulting in an ongoing
demand for smaller and lighter solutions. By eliminating the ferromagnetic
concentrator, the gradiometric MLX91235 achieves
a significantly smaller footprint than typical current sensor technologies and
eliminates hysteresis-related measurement errors. The differential measurement of
the magnetic field between two internal sensing elements provides accurate current
feedback, as well as ensuring stray field effects are eliminated. Featuring a 500
kHz bandwidth and 2 μs response time, the sensor is ideally suitable for high-speed
applications, such as motor control and converter applications.

Digital architecture & accuracy

The MLX91235’s intelligent digital architecture elevates the sensor’s
offering, ensuring high measurement accuracy and allowing for the incorporation of
several key functions that help to enhance development, calibration, and system
integration. When dealing with intrinsic non-linearities, analog architectures often
rely on piecewise linear compensations. However, the MLX91235’s digital architecture
offers the ability to implement more precise and sophisticated compensation,
resulting in a more accurate and smoother output. The fully digital-based thermal
compensation further ensures that the MLX91235 provides the highest accuracy
measurement across its entire working conditions.

Open calibration via SPI

The device’s ‘open’ calibration is configured through a standard serial
peripheral interface (SPI) allowing for configuration in situ via any
microcontroller unit (MCU). Compared to analog coreless sensors, digital calibration
provides a more direct and significantly quicker experience, enabling easy
adjustment of elements like digital gain correction.

Over-current detection & temperature monitoring

The built-in 16-bit over-current detection (OCD) allows for asymmetric
thresholds and includes two configurable threshold ranges. It features a
configurable detection time with a minimum duration of 2 μs and an optional debounce
strategy. This strategy helps to avoid false positives in harsher electromagnetic
compatibility (EMC) environments. Further enhancing its value, the MLX91235 also
includes a 10-bit temperature feedback mechanism, enabling accurate measurement of
junction temperature that is transmitted through a high-speed SPI output.

Functional safety & self-test

The MLX91235 is ISO 26262 compliant as an ASIL B Safety Element out of
Context (SEoOC). Going beyond ASIL B requirements, it also incorporates a
sophisticated built-in self-test feature that can be triggered via SPI. This
functionality allows the sensor to report critical information like temperature,
under-voltage, and mechanical stress. Notably, unlike conventional diagnostics, this
functionality encompasses the complete signal chain, up to the application MCU that
reads the sensor.

“Melexis has a rich history in current sensing technologies and the
coreless MLX91235 is our next step,” said Bruno Boury, Product Line Director at
Melexis. He continued “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.”

Designed to meet the needs of automotive and industrial current sensing
applications, the MLX91235 supports PCB and busbar current sensing in systems such
as inverters, low-voltage DC-DC converters, chargers, electrically heated catalysts
(EHCs), BMSs, smart pyro fuses, and more.

MLX91235 engineering samples and DVK91235 development
kits are available now. The product is expected to be fully qualified by mid-2025.
To request samples or development kits, please contact your local Melexis
representative or visit www.melexis.com/MLX91235.


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