Magnetic Field Sensor Self-Calibration via Adjustable Time Constant
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Solution Overview
Problem
Conventional magnetic field sensors lack the ability to perform fast self-test and self-calibration without reducing resolution or increasing noise levels, and they typically require shutdown from regular sensing mode to perform these functions, which can lead to inaccuracies and inefficiencies.
Innovation Solution
The development of magnetic field sensors with built-in self-test and self-calibration circuits that allow for rapid testing and calibration within a short time period while maintaining resolution and minimizing noise, even during regular sensing operations, using techniques such as time multiplexing and switched capacitor circuits to control sensitivity and offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional self-test and self-calibration circuits are used, then the magnetic field sensor can be tested and calibrated, but the sensor must shut down from regular sensing mode and the process takes a long time with single bandwidth
Solution Approach 1:
The patent implements periodic action by using a clock frequency generator to produce multiple redistribution clock frequencies at different times, enabling the self-test and self-calibration to occur in periodic intervals rather than requiring a complete shutdown. This allows the sensor to maintain operational status while periodically performing calibration functions.
Solution Approach 2:
The patent applies dynamics by making the time constant adjustable rather than fixed. The switched capacitor circuit allows the time constant to be dynamically changed between different values (first and second time constants) depending on the operational mode, enabling fast self-test when needed while maintaining accuracy during normal operation.
2Productivity
If the self-test or self-calibration is speeded up by increasing bandwidth, then the self-test rate increases, but the magnetic field sensor accuracy decreases and output noise level increases
Solution Approach 1:
The patent uses dynamics by implementing an adjustable time constant through a switched capacitor circuit. This allows the system to dynamically select between a first time constant during self-test mode (enabling faster testing) and a second time constant during normal operation (maintaining high accuracy and low noise), thus resolving the contradiction between test speed and measurement precision.
Solution Approach 2:
The patent applies parameter changes by modifying the time constant parameter based on operational requirements. The clock frequency generator produces different redistribution clock frequencies that correspond to different time constants, allowing the system to optimize the time constant parameter for either fast self-testing or high-precision measurement as needed.
3Device complexity
If a single time constant is used for self-calibration, then the circuit is simpler, but the sensor cannot achieve both fast self-test and high accuracy simultaneously
Solution Approach 1:
The patent applies universality by designing a switched capacitor circuit that can serve multiple functions: it acts as a filter during normal operation with one time constant, and as a fast-response circuit during self-test with another time constant. This multi-functional design allows a single circuit structure to achieve both fast self-testing and high accuracy without requiring separate dedicated circuits for each function.
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
Enables fast and accurate self-testing and self-calibration of magnetic field sensors without compromising resolution or increasing noise levels, allowing for continuous operation and improved reliability.
Implementation Method 1
a switched capacitor circuit having an integrator with a selectable time constant
Implementation Method 2
Hall effect elements generate an output voltage proportional to a magnetic field
Implementation Method 3
magnetoresistance elements change resistance in proportion to a magnetic field
Data Source
Figure 1~1A
Figure 2
Figure 2A~2C
AI summary
A magnetic field sensor includes a reference-field-sensing circuit channel that allows a self-test or a self-calibration of the circuitry of the magnetic field sensor. The self-test or the self calibration can have at least two different bandwidths that provide a respective at least two different rates of self-test or self-calibration.