Introducing MLX90427 position sensing for steer-by-wire

8th May 2024
Paige West

Melexis has expanded its magnetic position sensor portfolio with the introduction of the MLX90427, a product tailored for embedded position sensor applications that require high levels of functional safety.

In addition to offering customer stray field immunity and EMC robustness, the MLX90427 features a cost-effective SPI output with four distinct modes, including rotary, joystick, rotary stray field with internal angle computation, and a mode for raw data output. This sensor is particularly suited for steer-by-wire applications.

As the automotive industry increasingly moves toward the digitisation of control systems to support vehicle electrification and advanced autonomous capabilities, the demands on sensors have evolved. Position sensors are essential in systems like steer-by-wire, where there is no mechanical connection between the steering wheel and the steering mechanism, requiring sensors that offer reliability, functional safety, and accuracy. The heightened requirements for sensors in electric vehicles call for EMC robustness and stray field immunity, while also being cost-effective and easy to integrate.

The MLX90427 represents the next generation in Melexis' magnetic position sensing technology. Leveraging Melexis' experience in automotive Hall effect sensing, this product meets the stringent current and future demands of the automotive industry. It incorporates the Triaxis hall magnetic sensing element, sensitive to three components of flux density (Bx, By, and Bz), enabling precise movement detection of any nearby magnet. This capability is enhanced by an integrated analog-to-digital converter (ADC), a robust digital signal processor (DSP) for advanced signal processing, and an SPI output stage driver.

Operation and safety

The MLX90427 seamlessly transitions between its four operating modes, including a standard rotary mode with two performance ranges, a joystick mode for XYZ 3D position sensing, and a 360° stray field immune mode for continuous rotational feedback in electromagnetically noisy environments. This versatility allows the sensor to be used in a variety of vehicle applications such as steering, gearbox shifting, and broader human-machine interfaces like infotainment controls, simplifying vehicle design processes. Qualified to AEC-Q100 (Grade 0) and supporting ISO26262 ASIL C SEooC (up to ASIL D system level integration), the MLX90427 is ideal for safety-critical applications like steering columns, where it can be paired with sensors like the inductive sensing MLX90513 to achieve high levels of functional safety through heterogeneous redundancy.

Integration and communication

Designed for embedded applications, the MLX90427 features a high-speed full-duplex SPI output for communication and offers a 14-bit resolution output. Compatible with 5V and 3V3 applications, it operates across a wide temperature range from -40 to 160°C. Built-in self-diagnostics facilitate quick fault reporting, enhancing the safety of critical systems.

Karen Stinckens, Global Marketing Manager Position Sensors at Melexis, highlighted the sensor's significance: “Melexis has a long-standing reputation as the leading provider of sensors for safety-critical automotive systems, especially in areas like steering wheel position feedback,” she stated. “The MLX90427 builds on our previous successes and not only represents the next step in automotive position sensing but also offers a compelling solution for broader applications thanks to its advanced functionality and competitive price point.”

The MLX90427 is available in SOIC8 packaging starting in May, with a dual die TSSOP16 (fully redundant) variant set to launch in the fourth quarter of 2024.

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