New Stray-Field Robust HAL Position Sensor With SPC Interface

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This 3D position sensor allows active stray-field compensation and robust angular measurement for optimal steering-angle position detection

TDK Corporation has expanded its Micronas masterHAL® sensor family with the inclusion of HAL 3970, a new stray-field robust 3D HAL® position sensor. The sensor has highly accurate angular detection from 0 degrees to 360 degrees, linear position detection and uses Short PWM Code frames (SPC) to transmit the calculated position information, making it suitable for automotive and industrial applications

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 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, rolling counter amongst others are easily configurable. For example, HAL 3970 can be used for stray-field robust angle detection in steering-wheel position applications and long-stroke measurements in transmission systems or clutch applications

Accurate & Sophisticated Measurements

Each sensor within the HAL 39xy sensor family is based on the patented 3D HAL pixel cell technology. HAL 3970 uses a special array of Hall plates for high-accuracy measurement of vertical and horizontal magnetic-field components. Due to the sophisticated arrangement of these Hall plates, 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 features a powerful DSP, responsible for fast signal processing and an embedded microcontroller to perform interface configuration and supervision of functional safety-related tasks.

Primary characteristics like gain and offset, reference position, etc. can be adjusted to the magnetic circuitry by programming the non-volatile memory. 

Main features

  • Stray-field robust position detection (linear and rotary up to 360 degrees). 
  • Compensation of stray fields with gradients for applications with 180 degrees rotation.
  • Transmission of position and temperature information including rolling counter.
  • Supports SPC-enhanced 12-bit serial message format including temperature information.
  • Various SPC trigger modes (constant/variable length and short trigger pulse (point-2-point)).
  • Programming via sensor’s output pin at a minimum supply voltage.
  • Wide supply voltage range: 3.0 V to 16 V
  • Up to 16 kSps sampling frequency.
  • Wide ambient temperature range from -40 degrees Celsius up to 150 degrees Celsius.
  • Angular error: ±0.6 degrees
  • Magnetic field amplitude range: ±10 mT… ±130 mT

HAL 3970 is defined as SEooC (Safety Element out of Context) ASIL B-ready, according to ISO 26262. HAL 3970 will be available in eight-pin SOIC8 SMD package from the fourth quarter of 2020.


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