Drivers can use 3D position sensor for steering angle detection

Micronas masterHAL sensors from TDK now include a stray-field robust 3D HAL position sensor, the HAL 3970. It is designed for automotive and industrial applications and has angular detection, linear position detection and uses short PWM code frames (SPC) to transmit the calculated position information.

SPC is an enhancement of the standard SENT protocol according to SAE J2716. It enables data to be transmitted based on a trigger pulse sent by an external ECU, and it supports point-to-point connections as well as a single-wire bus mode with up to four sensors. Parameters such as unit time, frame format, trigger mode, slow channel format and rolling counter are configurable. For example, HAL 3970 can be used for stray-field robust angle detection in steering-wheel position applications.

HAL 3970 uses a special array of Hall plates for high-accuracy measurement of vertical and horizontal magnetic-field components. The sensor detects angles up to 360 degrees and suppresses external magnetic stray fields. Only a simple two-pole magnet is required to determine rotation angle. Ideally, the magnet should be placed above the sensitive area in an end-of-shaft configuration. The sensor also supports stray-field robust off-axis measurements.

The on-chip signal processing of HAL 3970 calculates the angle out of the magnetic-field components and converts this value into a digital output value. The sensor has a powerful DSP for fast signal processing and an embedded microcontroller which performs the interface configuration and supervision of the functional safety-related tasks.

Primary characteristics like gain and offset and reference position can be adjusted to the magnetic circuitry by programming the non-volatile memory. HAL 3970 is defined as SEooC (Safety Element out of Context) ASIL B-ready, according to ISO 26262. It is available in the eight-pin SOIC8 SMD package and samples will be available in Q4 2020.

TDK Corporation was established in 1935 to commercialise ferrite, a key material in electronic and magnetic products. TDK’s comprehensive portfolio features passive components such as ceramic, aluminium electrolytic and film capacitors, as well as magnetics, high-frequency and piezo and protection devices. The product spectrum also includes sensors and sensor systems such as temperature and pressure, magnetic, and MEMS sensors. In addition, TDK provides power supplies and energy devices and magnetic heads. Products are marketed under the product brands TDK, EPCOS, InvenSense, Micronas, Tronics and TDK-Lambda.

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