Magnetic Field Sensor Calibration Circuitry for Stress Stability
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Solution Overview
Problem
Magnetic field sensors face sensitivity changes due to temperature and mechanical stress, leading to undesirable variations in performance, which existing self-calibration techniques struggle to fully address.
Innovation Solution
A magnetic field sensor with self-calibration circuitry that generates both measured and reference magnetic field signals, using a calibration circuit to combine these signals and adjust gain or offset based on temperature, employing a Taylor series expansion for accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-calibration techniques are used to adjust sensitivity, then measurement precision is improved, but device complexity increases due to additional calibration circuitry
Solution Approach 1:
The patent combines the calibration magnetic field signal generation and measurement functions into the existing magnetic field sensor circuitry. The sensor measures both the calibration signal (generated by an on-chip coil) and the external magnetic field signal using the same sensing elements and signal processing paths, thereby achieving self-calibration without adding separate dedicated calibration hardware.
Solution Approach 2:
The magnetic field sensing elements serve multiple functions: they detect both the calibration magnetic field generated by the on-chip coil during calibration mode and the external magnetic field during normal operation mode. This multi-functionality allows a single sensor system to perform both calibration and measurement tasks without requiring separate dedicated sensors.
2Manufacturing precision
If calibration signals are generated using on-chip coils, then manufacturing precision is improved, but use of energy increases due to continuous calibration operations
Solution Approach 1:
The patent implements periodic calibration where the on-chip coil generates calibration magnetic field signals at specific intervals rather than continuously. The system switches between calibration mode (generating calibration signals) and measurement mode (detecting external magnetic fields), with the calibration occurring periodically to maintain accuracy while minimizing energy consumption associated with continuous calibration operations.
3Reliability
If temperature compensation is implemented to stabilize sensitivity, then reliability is improved, but device complexity increases due to additional temperature sensing and correction circuitry
Solution Approach 1:
The patent combines temperature compensation functionality with the existing calibration circuitry. The same on-chip coil that generates calibration magnetic fields is also used to generate temperature compensation signals by generating magnetic fields at different temperatures. The calibration circuit processes both calibration and temperature compensation signals through the same signal processing paths, achieving temperature compensation without adding separate dedicated temperature compensation hardware.
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 solution effectively stabilizes the magnetic field sensor's output by reducing sensitivity variations caused by temperature and mechanical stress, enhancing accuracy and reliability.
Implementation Method 1
at least one magnetic field sensing element configured to generate a measured magnetic field signal responsive to an external magnetic field
Implementation Method 2
a reference coil configured to carry a reference current to generate the reference magnetic field
Data Source
AI summary
A magnetic field sensor includes at least one magnetic field sensing element configured to generate a measured magnetic field signal responsive to an external magnetic field and to generate a reference magnetic field signal responsive to a reference magnetic field and a calibration circuit configured to divide the measured magnetic field signal by the reference magnetic field signal to generate a calibrated magnetic field signal. The calibrated signal has reduced susceptibility to stress influences.