Circular Vertical Hall Sensor Offset Reduction via Current Spinning
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Solution Overview
Problem
Magnetic field sensors using circular vertical Hall elements suffer from undesirable DC offsets, which affect their accuracy in measuring magnetic field angles and directions.
Innovation Solution
The implementation of a magnetic field sensor with a circular vertical Hall element configuration that includes a selection circuitry and current spinning phases to reduce DC offsets by sequencing through vertical Hall elements, using a combination of active and skipped contacts to optimize signal processing and minimize offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a circular vertical Hall element is used to sense magnetic field direction, then the sensor can provide angle measurement capability, but DC offset errors are generated that reduce measurement accuracy
Solution Approach 1:
The patent applies periodic action by sequentially switching current through different vertical Hall elements in a rotating pattern. The current spinning circuit cycles through multiple elements, allowing the system to sample offset voltages at different orientations and mathematically determine the magnetic field angle while compensating for DC offsets through the periodic sampling pattern.
Solution Approach 2:
The patent changes the parameter of current direction by sequentially reversing and rotating the current flow through different vertical Hall elements. By varying the current direction and which elements are active, the system can distinguish between magnetic field-induced voltage changes and inherent DC offset voltages, thereby reducing measurement errors.
2Measurement precision
If multiple vertical Hall elements are used in a circular configuration, then sensitivity to magnetic field direction is improved, but offset voltage variation between elements increases measurement complexity
Solution Approach 1:
The patent merges multiple vertical Hall elements into a unified circular vertical Hall structure where all elements share common electrical connections and are controlled by a single current spinning circuit. This integration allows the system to treat individual element offsets as part of a unified measurement model that can be compensated through mathematical processing rather than requiring separate compensation circuits for each element.
Solution Approach 2:
The patent implements self-service by using the sensor system itself to measure and compensate for its own DC offset errors. The current spinning sequence allows the system to automatically characterize its own offset voltages during normal operation and use this information to correct subsequent measurements, eliminating the need for external calibration equipment or complex external compensation circuits.
3Measurement precision
If current spinning is implemented to reduce DC offset, then offset error is reduced, but the circuit complexity increases
Solution Approach 1:
The patent segments the current path into multiple discrete switching states that can be sequentially activated. The current spinning circuit divides the operation into distinct phases where current flows through specific combinations of Hall elements, allowing simple switching elements to implement the complex offset reduction function without requiring a monolithic complex circuit design.
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 configuration significantly reduces DC offset errors, enhancing the accuracy and reliability of magnetic field angle measurements by equilibrating offset voltages and improving the transfer characteristic of the sensor, even under varying conditions such as temperature and mechanical stress.
Implementation Method 1
A magnetic field sensing element can be used to detect a direction of a magnetic field... A vertical Hall element tends to be responsive to magnetic field parallel to a surface of a substrate
Data Source
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AI summary
A magnetic field sensor with a plurality of magnetic field sensing elements is provided herein. The magnetic field sensor includes a circular vertical Hall (CVH) sensing element comprising a plurality of vertical Hall elements arranged over a common implant and diffusion region in a substrate, wherein the plurality of vertical Hall elements is configured to generate a plurality of magnetic field signals, each magnetic field signal responsive to a magnetic field. The magnetic field sensor further includes a sequence switches circuit coupled to the plurality of vertical Hall elements, wherein the sequences switches circuit is operable to select from among the plurality of vertical Hall elements. An associated method is also disclosed herein.