Inductive position sensor for ISO 26262-compliant EV motor controls

Inductive position sensor for ISO 26262-compliant EV motor controls

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By Christoph Hammerschmidt

Motor control designers are increasingly replacing Hall-effect position sensors and legacy magnetic resolver solutions with inductive alternatives that do not require expensive magnets and other heavy transformer-based components and can therefore be integrated on simple, compact circuit boards. Microchip Technology is expanding its line of inductive position sensors for EV motor control applications with the LX34070. The sensor offers differential outputs, fast sampling rates and functional safety features that make it ideal for meeting ISO 26262 ASIL-C classification.

“The LX34070 inductive position sensor enables lighter, smaller and more reliable motor controllers that can meet stringent safety requirements, reduce overall system costs and operate seamlessly and accurately in the interference-prone environment of DC motors, high currents and solenoids in a vehicle,” said Fanie Duvenhage, vice president of the Mixed Signal and Linear Analog Business Unit at Microchip. “Designers can use the sensor to optimize EV motor controls by coupling it with other functional safety-ready devices from Microchip, including our 8-bit AVR and PIC microcontrollers, our 32-bit microcontrollers and our dsPIC digital signal controllers.”

According to the manufacturer, the LX34070 offers numerous advantages over magnetic resolvers and linear voltage differential transformers (LVDTs) – at a fraction of the cost. By using conductive traces instead of transformer-based magnetic windings and coil structures, the new sensor has negligible size and mass compared to alternatives that weigh up to several hundred grams. The LX34070 also offers higher accuracy because it does not depend on magnet strength. And it improves robustness by actively suppressing stray magnetic fields. These and other features give designers more flexibility in placing the low-profile, lightweight PCB-based sensor in their EV motor controls.

PCB-based inductive position sensors use a primary coil to generate an alternating magnetic field coupled to two secondary coils. A small metallic target object disturbs the magnetic field so that each secondary coil receives a different voltage, the ratio of which is used to calculate absolute position. Microchip used this technology to mass-produce its first inductive sensor for automotive and industrial applications more than a decade ago. Numerous other devices based on this technology followed. The LX34070 now offers the same proven PCB materials, approaches and simplified, low-cost packaging for EV motor control and other applications that require its benefits of high speed and low latency.

Microchip is working closely with automotive OEMs and suppliers to help them meet ISO 26262 requirements. Functional safety packages provide exactly what is needed at various stages of the evaluation and development cycle, including certified safety manuals, Failure Mode Effect and Diagnostics Analysis (FMEDA) reports, and in some cases diagnostic software such as certified self-test libraries for relevant ASILs. Microchip also practices customer-driven obsolescence, continuing to supply devices as long as there is a need and all components are available. This eliminates the risk of forced redesign when a component unexpectedly reaches end-of-life (EOL).


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