Position sensors combine TMR and Hall elements for high accuracy, redundancy

Position sensors combine TMR and Hall elements for high accuracy, redundancy

New Products |
By Christoph Hammerschmidt

Allegro’s newest sensors combine the company’s vertical Hall technology (VHT) with cutting-edge tunneling magnetoresistance (TMR) technology in a single sensor package. This VHT + TMR offering is a superior heterogeneous redundant sensor solution and is an essential step toward enabling the reliability required for advanced levels of automation in vehicles.

Future automated and autonomous vehicles require advanced electric power steering (EPS) systems with precise motor control capabilities, as well as brake-by-wire or electromechanical braking systems with fast response time. Present-day systems commonly use giant magnetoresistance (GMR) or Hall-effect sensors. Compared to the GMR equivalents, Allegro’s innovative TMR-on-silicon technology offers improved resolution and accuracy, providing up to eight times greater sensitivity. Measured against traditional Hall-effect sensors, the improvement in resolution is even more pronounced.

The safe operation of a vehicle requires the highest level of diagnostic coverage in its safety-critical systems. Allegro’s VHT featured in the new A33110 and A33115 enables accurate safety checks, including low-field and missing-magnet detection. These high-resolution sensors are ASIL D-compliant, with heterogeneous redundancy reducing the likelihood of dependent failures by leveraging the best of both TMR technology and VHT.

As full autonomy comes closer to being a reality, automakers and Tier 1 suppliers are looking for position sensors that provide the greatest accuracy and safety while reducing system footprint and cost. “By integrating both vertical Hall and TMR elements in a single package, Allegro’s new line of sensors enable customers to meet those needs with a sensor that provides high resolution and heterogeneous redundancy along with integrated diagnostics,” said Scott Milne, Business Line Director for Position Sensors at Allegro, adding that he regards this new offering as a “game-changer” in the competitive environment.

The sensors provide magnetic angle sensing via both the primary (TMR) and secondary (vertical Hall) transducers, each of which are processed by two independent channels, each with independent regulators and temperature sensors. This unique configuration enables the high levels of safety and diagnostic coverage needed for automated driving, including on-chip channel-to-channel angle comparison and independent processing in digital signal paths, with no shared digital resources. Advanced algorithms in the A33110 and A33115 deliver the fast response time, independent gain/offset correction, angle calculation, and linearisation capabilities demanded by safety-critical ADAS applications. The A33115 also includes a turns counter that tracks motion in 90-degree increments and a low-power mode with a user-programmable duty cycle that reduces power consumption when the IC is in a key-off position.



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