TMR Sensor Offset Correction via PMA Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic sensors with tunnel magnetoresistive (TMR) sensing elements face accuracy and reliability issues due to signal offsets caused by variations in tunnel barrier layer area, etching non-uniformity, and magnetization alignment, which degrade the sensitivity and linear range of the sensors.
Innovation Solution
A circuit component applies an electrical signal with alternating signal levels across the tunnel barrier layer of the TMR sensing element, generating an offset-corrected sensor signal by controlling the perpendicular magnetic anisotropy (PMA) of the sensing element, thereby correcting for signal offsets and improving sensor accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TMR sensing elements are used without offset correction, then the device structure remains simple, but measurement precision deteriorates due to signal offsets from tunnel barrier layer variations and etching non-uniformity
Solution Approach 1:
The patent applies periodic switching of the electrical signal between first and second levels across the tunnel barrier layer. This periodic action modulates the perpendicular magnetic anisotropy (PMA) of the free layer, enabling the sensing element to operate at different operating points. By alternating between these levels, the system can measure and correct offset errors while maintaining a relatively simple device structure, thus improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The patent changes the electrical signal parameters (voltage level) applied across the tunnel barrier layer to modulate the PMA of the free layer. By varying the electrical signal between first and second levels, the magnetic anisotropy energy and consequently the magnetization direction of the free layer are changed. This parameter change enables offset correction by allowing the system to measure signals at different operating points and eliminate offset errors, thereby improving sensor accuracy.
2Measurement precision
If offset correction is implemented by applying alternating electrical signal levels, then measurement precision improves through offset elimination, but use of energy increases due to continuous signal switching
Solution Approach 1:
The offset correction is achieved through periodic switching of the electrical signal between first and second levels. This periodic action allows the system to acquire measurement data at different operating points and calculate offset corrections. The energy consumption is managed by implementing the switching only when needed for offset correction rather than continuous switching, thus achieving offset elimination while controlling energy usage.
Solution Approach 2:
The patent performs offset correction measurements preliminarily or periodically rather than continuously. By implementing the alternating signal levels and offset correction algorithm at specific intervals or during calibration phases, the system achieves accurate offset compensation while minimizing continuous energy consumption. This preliminary action approach allows the sensor to operate at lower power during normal measurement while periodically correcting offsets.
3Measurement precision
If the electrical signal level is increased to improve signal-to-noise ratio, then measurement precision improves, but the tunnel barrier layer may experience increased stress and reliability deteriorates
Solution Approach 1:
Instead of using a single high electrical signal level to improve signal-to-noise ratio, the patent employs parameter changes by switching between multiple signal levels (first and second levels). This allows the system to achieve better effective signal-to-noise ratio through differential measurement and offset correction while keeping individual signal levels moderate, thus avoiding excessive stress on the tunnel barrier layer and maintaining reliability.
Solution Approach 2:
The patent converts the potential harm of high electrical stress on the tunnel barrier layer into a benefit by using moderate signal levels in combination with periodic switching and offset correction algorithms. The moderate signal levels prevent degradation of the tunnel barrier layer, while the switching and correction methodology maintains or even improves measurement precision through better noise rejection and offset elimination.
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 method effectively corrects signal offsets in magnetic sensors by modulating the electrical signal across the tunnel barrier layer, enhancing the sensitivity and linear range of the TMR sensing elements, leading to improved accuracy and reliability of magnetic field detection.
Implementation Method 1
Deviations in the magnetization of the free layer result in changes in resistance through the magnetic tunnel junction, a characteristic which can be sensed in order to, in the example of a magnetic field sensor, detect and quantify an externally applied magnetic field. This phenomenon is referred to as the tunneling magnetoresistance (TMR) effect.
Implementation Method 2
generating an offset-corrected sensor signal by controlling the perpendicular magnetic anisotropy (PMA) of the sensing element
Data Source
AI summary
In some implementations, a magnetic sensor may apply an electrical signal across a tunnel barrier layer of a tunnel magnetoresistive (TMR) sensing element. The electrical signal may have a first signal level during a first time period and a second signal level during a second time period. The second signal level may be different from the first signal level. The magnetic sensor may generate an offset-corrected sensor signal based on a sensor signal that results from applying the electrical signal across the tunnel barrier layer of the TMR sensing element.