Non-magnetic sensors developed for accurate motor position monitoring including for ISO 26262 compliant EV motor control applications
Developers of motor control systems are rapidly replacing Hall Effect position sensors and older magnetic resolver solutions with inductive alternatives that eliminate expensive magnets and other heavy transformer-based structures so they can be integrated onto simple, compact printed circuit boards (PCBs).
Responding to this and extending its broad range of inductive position sensors into the EV motor control market, Microchip Technology is now also supplying the LX34070 IC that has been purpose-built for EV motor control applications. It includes differential outputs, fast sample rates and features that make it functional-safety-ready for ISO 26262 compliance in the Automotive Safety Integrity Level–C (ASIL–C) classification.
According to Fanie Duvenhage, vice president of Microchip’s mixed signal and linear analogue business unit, the LX34070 inductive position sensor enables lighter, smaller, more reliable motor control systems that meet stringent safety requirements, reduce overall system costs and can operate seamlessly and precisely in the noisy environment of an automobile’s DC motors, high currents and solenoids.
“Designers can use the LX34070 to further streamline EV motor control designs by pairing it with other functional-safety-ready Microchip devices including our 8-bit AVR and PIC microcontrollers, our 32-bit microcontrollers, and our dsPIC digital signal controllers,” he says.
Inductive Sensor Advantage
The LX34070 inductive position sensor solution offers numerous advantages compared to magnetic resolvers and Linear Voltage Differential Transducers (LVDTs), at a fraction of the cost. By using PCB traces rather than transformer-based magnetic windings and coil structures, the LX34070 device has negligible size and mass compared to alternatives that weigh as much as a half a kilogramme.
Accuracy is improved since the LX34070 does not depend on magnetic strength, and the device improves robustness by actively rejecting stray magnetic fields. These and other features give designers greater flexibility over where they can place the thin, lightweight PCB-based LX34070 device in their EV motor control designs.
PCB-based inductive position sensors use a primary coil to generate an AC magnetic field that couples with two secondary coils. A small metal target object disturbs the magnetic field so that each secondary coil receives a different voltage whose ratio is used to calculate absolute position.
Using these techniques, Microchip introduced its first high-volume inductive sensor for automotive and industrial applications over a decade ago and has many variants in volume production. The LX34070 now brings the same proven PCB materials, approaches and simplified, low-cost packaging to EV motor control and other applications that need its high-speed and low-latency benefits.
ISO 26262 standard certification
The sensor company is continuing to work closely with OEMs and suppliers in the global automotive industry in order to support their ISO 26262 compliance needs. The company’s functional safety packages give them what they need at various stages of the evaluation and design 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.
The company also practices customer-driven obsolescence, with Microchip continuing to supply devices as long as there is demand and all components are available, removing the risk of a forced redesign because a part may unexpectedly enter end-of-life (EOL).