Magnetic Field Sensor with Permanent Magnet Biasing
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Solution Overview
Problem
Existing magnetic field sensors face challenges in achieving low power consumption and cost-effective, three-axis sensing capabilities without detrimental perming effects, especially in handheld and miniaturized applications where power efficiency and reliability are critical.
Innovation Solution
The implementation of a magnetic field sensor with sensor bridge designs that incorporate multiple orientations of reference magnetization and out-of-plane biasing of the sense layer, utilizing a single permanent magnet layer for Z-axis sensing to eliminate the need for flux guides, enabling ultra-low power consumption and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flux guides are used for Z-axis sensing, then three-axis sensing capability is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes the flux guide component from the sensor structure entirely. Instead of using flux guides to concentrate and direct magnetic flux for Z-axis sensing, the invention employs a permanent magnet layer integrated directly with the sense element, eliminating the need for separate flux guiding structures and reducing overall device complexity
Solution Approach 2:
The permanent magnet layer is merged with the sense element structure, combining the biasing function and sensing function into a unified architecture. This integration eliminates the need for separate flux guide components and reduces the number of manufacturing steps required
2Measurement precision
If multiple permanent magnet layers are used for biasing, then sensing accuracy is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The single permanent magnet layer performs multiple functions: it provides out-of-plane magnetic biasing for the sense layer, enables Z-axis sensing capability, and establishes the operating point for the magnetoresistive element. This multi-functionality eliminates the need for multiple separate permanent magnet layers while maintaining sensing accuracy
Solution Approach 2:
The patent changes the magnetization orientation parameter of the permanent magnet layer to be substantially perpendicular to the plane of the sense element, which enables out-of-plane biasing and Z-axis sensing. This parameter change allows a single layer to achieve what would traditionally require multiple layers with different orientations
3Adaptability or versatility
If conventional magnetic field sensors are used, then three-axis sensing is achieved, but power consumption increases
Solution Approach 1:
The permanent magnet layer provides passive, continuous magnetic biasing without requiring external power input. The magnetoresistive sense element responds passively to magnetic field changes, enabling sensing operation with minimal power consumption compared to active sensing mechanisms
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 solution allows for reliable, low-power, multiple-axis magnetic field sensing without perming effects, enhancing sensitivity and reducing costs while maintaining accurate axis alignment and minimizing noise.
Implementation Method 1
a permanent magnet layer spaced apart from the magnetoresistive sense elements and having a single magnetic orientation. The permanent magnet layer magnetically biases the initial orientation of the sense magnetization
Implementation Method 2
magnetoresistive sense elements located in a plane of the magnetic field sensor and sensitive to changes in an external magnetic field
Data Source
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AI summary
A magnetic field sensor comprises a sensor bridge having multiple sensor legs. Each sensor leg includes magnetoresistive sense elements located in a plane of the magnetic field sensor. Each sense element comprises a pinned layer and a sense layer. The pinned layer has a reference magnetization oriented parallel to the plane and the sense layer has a sense magnetization oriented out-of-plane. A permanent magnet layer may be spaced apart from the sense elements which magnetically biases the sense magnetization of the sense layer into an out-of-plane direction that is non-perpendicular to the plane of the sensor. The sense magnetization is orientable from the out-of-plane direction toward the plane of the sensor in response to an external magnetic field. The permanent magnet layer enables detection of the external magnetic field in a sensing direction that is also perpendicular to the plane of the magnetic field sensor.