Z-Axis Magnetic Sensor Self-Test via Coil and Bridge
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Solution Overview
Problem
Current Z-axis magnetic field sensors lack the ability to perform a true self-test, as existing self-test capabilities exclude the interaction between out-of-plane elements and in-plane detectors, limiting the evaluation of sensor functionality and sensitivity calibration.
Innovation Solution
A magnetic field sensor with a current carrying coil structure surrounding in-plane magnetoresistive sense elements, producing a vertical magnetic field component to stimulate all components of the Z-axis sensor, and a Wheatstone bridge configuration for common mode rejection of parasitic lateral field components, enabling interaction testing between flux guides and in-plane sense elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-test capability is implemented in Z-axis magnetic field sensors using prior art methods, then sensor operation can be tested, but the interaction between out-of-plane elements and in-plane detectors cannot be evaluated
Solution Approach 1:
The sensor is divided into functional segments: out-of-plane flux guide elements and in-plane detector elements. The self-test capability is implemented by separately addressing these segments through a coil structure that generates magnetic field components oriented to stimulate each segment's interaction, enabling comprehensive evaluation of the complete sensor architecture.
Solution Approach 2:
A coil structure is introduced that generates magnetic field components in multiple dimensions (out-of-plane and in-plane components). This dimensional approach allows the self-test to stimulate the interaction between out-of-plane flux guides and in-plane detectors, enabling complete sensor evaluation that prior single-dimension methods could not achieve.
2Measurement precision
If a coil structure is added to enable complete self-test capability, then interaction between flux guides and sense elements can be tested, but device complexity increases
Solution Approach 1:
The coil structure is designed to serve multiple functions: it generates out-of-plane magnetic field components to stimulate flux guides, generates in-plane magnetic field components to stimulate detectors, and enables complete self-test capability. This multi-functionality reduces the need for separate test structures and minimizes overall device complexity.
Solution Approach 2:
The sensor package performs self-diagnosis and self-characterization using the coil structure and associated circuitry integrated within the same package. The self-test capability allows the sensor to evaluate its own functionality, sensitivity, and linearity without requiring external testing equipment, thereby simplifying the overall system architecture.
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 a complete evaluation of Z-axis magnetic field sensors by testing the interaction between flux guides and in-plane sense elements, enhancing sensor functionality and sensitivity calibration.
Implementation Method 1
A magnetic field sensor with Z-axis self-test capability includes a current carrying coil structure surrounding in-plane magnetoresistive sense elements. The coil structure produces a vertical (i.e., out-of-plane) magnetic field component across the active sensor region to properly stimulate all components of the Z-axis magnetic sensor.
Implementation Method 2
A magnetic field sensor with Z-axis self-test capability includes a current carrying coil structure surrounding in-plane magnetoresistive sense elements.
Data Source
AI summary
A magnetic field sensor includes in-plane sense elements located in a plane of the magnetic field sensor and configured to detect a magnetic field oriented perpendicular to the plane. A current carrying structure is positioned proximate the magnetic field sensor and includes at least one coil surrounding the in-plane sense elements. An electric current is applied to the coil to create a self-test magnetic field to be sensed by the sense elements. The coil may be vertically displaced from the plane in which the sense elements are located and laterally displaced from an area occupied by the sense elements to produce both Z-axis magnetic field components and lateral magnetic field components of the self-test magnetic field. The sense elements are arranged within the coil and interconnected to cancel the lateral magnetic field components, while retaining the Z-axis magnetic field components to be used for self-test of the magnetic field sensor.