Magnetic Field Sensor Trimming via Integrated Coil Compensation
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Solution Overview
Problem
Magnetic field sensors face challenges in accurately trimming sensitivity due to limitations in generating precise differential magnetic fields, leading to errors in sensitivity measurement and temperature coefficient trimming, especially when external fields are present.
Innovation Solution
The integration of coils with magnetic field sensing elements, such as Hall elements, allows for directional current flow to enhance trimming precision by compensating for external field effects, using a H-bridge coil driver and averaging normalized coil sensitivities for consistent sensitivity measurement across varying external fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment is used to generate magnetic fields for sensor trimming, then the trimming process can be performed, but the accuracy is limited due to inability to generate precise differential magnetic fields
Solution Approach 1:
The patent integrates test coils directly with the magnetic field sensing elements on the same substrate, merging the sensing and testing functions into a single integrated structure. This eliminates the need for separate external test equipment and enables precise differential magnetic field generation for accurate sensitivity trimming.
Solution Approach 2:
The integrated coils serve as intermediaries that generate controlled magnetic fields directly at the sensing element location. These coils act as a mediator between the test system and the sensor, providing precise differential magnetic fields that enable accurate sensitivity measurement and trimming without requiring complex external equipment.
2Reliability
If external magnetic fields are present during trimming, then the sensor can operate in real-world conditions, but measurement errors occur due to inability to compensate for external field effects
Solution Approach 1:
The patent employs feedback mechanisms where the output signal from the sensing element is fed back through the integrated coils to generate compensating magnetic fields. This feedback loop enables real-time compensation for external field effects, allowing accurate sensitivity trimming even when external magnetic fields are present during operation.
Solution Approach 2:
The integrated coils generate preliminary compensating magnetic fields that counteract external field effects before they can affect the sensing element. By applying opposite-polarity fields through the coils, the system pre-compensates for external magnetic field disturbances, ensuring accurate measurements despite real-world operating conditions.
3Measurement precision
If directional current flow is used in integrated coils, then trimming precision is enhanced, but the device complexity increases
Solution Approach 1:
The patent implements dynamic control of current flow direction in the integrated coils, allowing the system to switch between different current polarities based on the trimming requirements. This dynamic capability enables precise control of the magnetic field direction and magnitude, enhancing trimming precision while managing device complexity through programmable control.
Solution Approach 2:
The coil driver employs periodic switching of current direction to achieve precise trimming. By alternately applying positive and negative current pulses to the integrated coils, the system creates controlled magnetic field cycles that enable accurate sensitivity adjustment. This periodic action allows precise trimming through systematic variation of field conditions.
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 approach enables accurate trimming of magnetic sensor sensitivity within 1% accuracy, overcoming limitations of external test equipment and ensuring reliable performance across different external field conditions.
Implementation Method 1
The integration of coils with magnetic field sensing elements, such as Hall elements, allows for directional current flow to enhance trimming precision by compensating for external field effects
Implementation Method 2
Hall effect elements generate an output voltage proportional to a magnetic field
Data Source
Figure 1
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Figure 3A~3C
AI summary
Method and apparatus for trimming a magnetic field sensor having a first magnetic field sensing element. In embodiments, trimming includes the use of a curve for normalized sensitivity of the first magnetic field sensing element derived from a first curve corresponding to current through a coil in a first direction at a first time to produce a field affecting the first magnetic field sensing element versus an external field and a second curve corresponding to current through the coil in a second direction opposite to the first direction at a second time to produce a field affecting the first magnetic field sensing element versus an external field.