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3D Hall-Effect Position Sensor Offers Stray-Field Compensation

Nov. 21, 2018
The wide range of automotive applications for the device include brake and accelerator position detection, gear-shift position detection, and steering-angle detection.

The increasing requirement for stray-field compensation is creating new challenges for the design of magnetic sensors. Paired with increased functional safety requirements, as per ISO 26262 for autonomous driving functions, and the growing need for digital interfaces (e.g. SENT, SPI, PSI5), low-power modes, and 3D capability, the market clearly demands a kind of sensor that offers greater functionality and flexibility. At the recent electronicaTDK introduced a 3D Hall-effect position sensor family designated Micronas HAL 39xy. According to the company, it’s unique in that it offers both stray-field compensation and a highly flexible architecture.

The new HAL39xy sensors offer four different measurement modes in a single device. The obvious benefit of such a feature is that customers only have to qualify one device instead of various different hardware versions. The new sensors are well-suited for a wide range of applications, including all kind of valves and actuators, selectors and gear shifters, pedal-position detection, position detection in transmission systems, steering-angle detection, or chassis-position detection.

The four different measurement modes are:

  • Linear position detection with stray-field compensation
  • Rotary 360° angle detection with stray-field compensation
  • Rotary 180° angle detection with stray-field compensation, including gradient fields
  • Real 3D magnetic field measurement (BX, BY, BZ)

Each mode uses a different combination of Hall plates to enable best performance.

The HAL 39xy family presents a wide range of configuration possibilities. Each sensor features a digital signal processor (DSP) and an embedded microcontroller (see figure). The DSP is mainly responsible for the fast signal processing (angle calculation, compensation, etc.), while the microcontroller performs overall scheduling, interface configuration, and supervision of the functional safety-related tasks. Customized firmware can be developed for both blocks.

In addition to a patented Hall plate array, the Micronas HAL 39xy Hall-effect position sensor family features a DSP and an embedded microcontroller, both with configurable firmware.

Together with the flexible Hall front-end, this enables customers to realize new kinds of applications. For example, this can involve customized signal processing or support for new interface standards. TDK notes that the architecture of the HAL 39xy makes it easy for customers to develop new solutions using fast prototyping techniques. It also facilitates adaptation to changes in interface standards such as SENT and PSI5.

In automobiles, the stray-field requirement is a big challenge for magnetic-field sensors. Motors and power lines in hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) carry high currents and can generate magnetic fields that interfere with magnetic-field sensors.

A modern Hall-effect sensor must now offer robust stray-field immunity conforming to the latest ISO 11452-8 standard and related OEM requirements. Here, the stray-field immunity concept is based on an array of vertical and horizontal Hall plates. The heart of the sensor is the patented 3D Hall pixel cell. With this flexible sensor array, design engineers can select the best stray-field concept for a given measurement task.

First samples will be available in the first quarter 2019. Further sensor variants, such as a dual-die version with redundancy functionality or with integrated capacitors, are under development.

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