AMR Angle Sensor Die for Stray Field Immunity
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Solution Overview
Problem
Anisotropic magneto-resistive (AMR) angle sensors face accuracy degradation due to interference from stray magnetic fields, particularly in environments like automobile engine compartments, where transient electrical currents generate strong magnetic interference, exceeding industry standards for immunity.
Innovation Solution
The implementation of an AMR angle sensor package featuring a plurality of AMR sensors on a single die, coupled with magnets generating orthogonal in-plane magnetic fields, reduces susceptibility to stray magnetic fields by combining angle outputs and using a single analog front end for signal conditioning and power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single AMR sensor is used, then the device complexity is low, but the immunity to stray magnetic fields deteriorates and measurement precision degrades
Solution Approach 1:
The invention divides a single sensor function into multiple AMR sensors arranged in specific geometric patterns (octagonal, rectangular, or triangular configurations). Each sensor measures magnetic field components from different orientations, and their outputs are combined through signal processing to achieve enhanced immunity to stray magnetic fields while maintaining reasonable device complexity through integrated circuit implementation.
2Reliability
If multiple AMR sensors are used to improve stray field immunity, then reliability improves, but device complexity increases
Solution Approach 1:
The invention merges multiple AMR sensors and their signal processing functions into a single integrated sensor die. The plurality of AMR sensors are fabricated on the same substrate with integrated readout circuitry that combines the outputs of individual sensors to produce a unified angle measurement signal. This integration approach maintains improved stray field immunity while preventing excessive device complexity by consolidating multiple sensor elements and their processing functions into one compact unit.
3Measurement precision
If multiple AMR sensors with combined outputs are used, then measurement precision improves under stray fields, but manufacturing precision requirements increase
Solution Approach 1:
The invention implements different geometric arrangements (octagonal, rectangular, or triangular patterns) optimized for specific measurement requirements and stray field conditions. Each sensor within the array is positioned and oriented with specific local characteristics to detect particular magnetic field components. The readout circuitry is designed to process signals from sensors with these differentiated local qualities, allowing the system to achieve high measurement precision while accommodating manufacturing tolerances through the distributed nature of the sensor array.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the sensors' immunity to stray magnetic fields, maintaining accuracy within ±0.1 degree even in the presence of up to 4 mT stray magnetic fields, aligning with industry standards for reduced angular displacement loss.
Implementation Method 1
Anisotropic magneto-resistive material changes the value of its electrical resistance in response to a change in an externally applied magnetic field—for example, in response to a change in direction of the externally applied magnetic field
Implementation Method 2
each of the plurality of AMR angle sensors comprising a first Wheatstone bridge and a second Wheatstone bridge
Data Source
AI summary
Some embodiments are directed to an anisotropic magneto-resistive (AMR) angle sensor die. The die comprises a plurality of AMR angle sensors, each of the plurality of AMR angle sensors comprising a first Wheatstone bridge and a second Wheatstone bridge, wherein an angle position output of the sensor die includes a combination of angle position outputs of each of the plurality of AMR angle sensors.