TMR Angular Sensor Bridge With Analog Tangent Output
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Solution Overview
Problem
Existing angular magnetic sensors using TMR-based elements face challenges with temperature dependence, limited angle range, and high power consumption due to the use of analog-digital converters and iterative algorithms, leading to inaccurate determination of external magnetic field orientation.
Innovation Solution
A two-dimensional analog angular magnetic sensor device comprising a full-bridge configuration of TMR elements with an integrated analog circuit that generates tangent or cotangent output voltages, independent of TMR ratio, and includes a temperature-stable design for a wide angle range, reducing power consumption and die size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TMR-based elements are used in angular magnetic sensors, then sensitivity and signal-to-noise ratio are improved, but temperature dependence increases
Solution Approach 1:
The sensor divides the measurement function into four separate TMR elements arranged in a full-bridge configuration, with each element having its magnetization oriented at different angles (0°, 45°, 90°, 135°). This segmentation allows the temperature-dependent responses of individual elements to cancel out when combined in the differential bridge output, resolving the contradiction between high sensitivity and temperature stability.
Solution Approach 2:
The invention changes the magnetization orientation parameters of the TMR elements from conventional configurations to specific angles (0°, 45°, 90°, 135°), and modifies the bridge configuration to achieve tangent or cotangent output characteristics. This parameter change enables the system to maintain temperature independence while preserving the high sensitivity inherent to TMR elements.
2Measurement precision
If analog-digital converters and iterative algorithms are used, then measurement accuracy is improved, but power consumption and device complexity increase
Solution Approach 1:
The invention replaces the conventional digital processing system (analog-digital converters and iterative algorithms) with an analog computational approach. The full-bridge TMR circuit directly computes the tangent or cotangent of the magnetic field angle through its inherent differential voltage output, eliminating the need for power-hungry ADCs and iterative calculation algorithms while maintaining measurement accuracy.
Solution Approach 2:
The TMR-based full-bridge circuit performs the angle calculation function autonomously through its analog voltage output characteristics. The circuit self-generates the tangent or cotangent output that directly represents the magnetic field orientation, without requiring external digital processing resources, thereby reducing overall system power consumption and complexity.
3Ease of operation
If conventional TMR bridge configuration is used, then sinusoidal output is achieved, but angle determination accuracy is limited
Solution Approach 1:
The invention changes the magnetization orientation parameters of the TMR elements from conventional configurations to specific angles (0°, 45°, 90°, 135°), and modifies the bridge configuration to achieve tangent or cotangent output characteristics instead of sinusoidal output. This parameter change provides a more accurate angle determination function, especially for small angles, while maintaining ease of operation through direct voltage output.
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
The sensor provides accurate, fast, and temperature-stable measurement of magnetic field orientation over a wide range with improved signal-to-noise ratio and reduced power consumption.
Implementation Method 1
Sensor technologies using a magnetic tunnel junctions (MTJ) based on tunnel magnetoresistance (TMR) effect excel among rival technologies based on anisotropic magnetoresistance (AMR) effect, giant magnetoresistance (GMR) effect and Hall effect
Data Source
AI summary
A two-dimensional analog angular magnetic sensor device for measuring an orientation of an external magnetic field, comprising at least a magnetic sensor, comprising a plurality of tunnel magnetoresistance (TMR) elements arranged in a full-bridge configuration and configured to provide a sine output voltage: VSIN=A·sin θ·Vdd, or configured to provide a cosine output voltage VCOS=A·cos θ·Vdd, wherein A is parameter depending on the TMR ratio of the TMR element and Vdd is a bias voltage inputted to the magnetic sensor. The magnetic sensor device further comprises an analog circuit configured to generates a circuit output voltage and electrically connected to the magnetic sensor such as that the magnetic sensor device generates a device output voltage that follows one of: a tangent output voltage VTAN:Vout=K·Vdd·VTAN=K·Vdd·tan θ, where K is a constant; or a cotangent output voltage (VCOTAN):Vout=K·Vdd·VCOTAN=K·Vdd·cotanθ.