Hall Effect Circuit Stress Compensation via Epitaxial Resistor
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Solution Overview
Problem
Hall effect elements experience sensitivity changes due to stresses on the substrate, which are not effectively compensated for by existing technologies, leading to variations in differential output signals.
Innovation Solution
An electronic circuit with a current generator and resistors in an epitaxial layer that adjusts the drive current based on stress changes, using buried structures and pickups to generate a reference current that compensates for substrate stress, thereby stabilizing the sensitivity of the Hall effect element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stable current source or current sink is used to generate the drive current, then the drive current stability is improved, but the sensitivity changes due to substrate stress cannot be compensated
Solution Approach 1:
The patent implements a feedback mechanism where the resistance of the first resistor, which changes in accordance with substrate stress, is used to automatically adjust the drive current through the current generator. This feedback loop compensates for stress-induced sensitivity changes by modifying the drive current in response to stress conditions, thereby maintaining measurement precision while preserving drive current stability through the stable reference voltage.
Solution Approach 2:
The patent changes the parameter of drive current amplitude dynamically by linking it to the stress-dependent resistance of the first resistor. As substrate stress changes, the resistance changes, which in turn modifies the drive current amplitude to compensate for sensitivity variations. This parameter change approach allows the system to adapt to stress conditions while maintaining stable operation through the reference voltage.
2Measurement precision
If temperature sensing and correction is implemented, then temperature-induced sensitivity changes are corrected, but stress-related sensitivity changes remain uncompensated
Solution Approach 1:
The first resistor serves multiple functions: it acts as a current-setting element in the drive current path and simultaneously serves as a stress-sensing element whose resistance changes with substrate stress. This multi-functionality eliminates the need for separate stress sensing and compensation circuits, reducing device complexity while providing comprehensive sensitivity correction for both temperature and stress effects.
Solution Approach 2:
The system uses the substrate stress itself to generate the compensation signal. The stress-induced resistance change in the first resistor automatically adjusts the drive current to compensate for sensitivity variations, without requiring external stress sensors or complex control circuits. The stress condition directly serves the compensation function through the inherent piezoresistive effect.
3Measurement precision
If the drive current amplitude is increased to improve signal amplitude, then the differential output signal amplitude is improved, but stress-induced sensitivity changes are amplified
Solution Approach 1:
The patent makes the drive current dynamic by linking it to the stress-dependent resistance of the first resistor. The drive current amplitude automatically adjusts in response to substrate stress conditions, allowing the system to optimize signal amplitude under different stress states. This dynamic adjustment maintains sensitivity stability by compensating for stress effects while improving differential output signal amplitude through appropriate current levels.
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 compensates for sensitivity changes caused by substrate stress, maintaining stable differential output signals and reducing the impact of stress-related variations on Hall effect element sensitivity.
Implementation Method 1
a first resistor for receiving a reference voltage resulting in a reference current passing through the first resistor, the reference current related to the drive current, the first resistor disposed in the epitaxial layer, wherein a resistance of the first resistor, the reference current, and the drive current change in accordance with changes of a stress in the semiconductor substrate
Implementation Method 2
A typical planar or horizontal Hall effect element is a four terminal device for which a drive current (a DC current) is passed between two opposing ones of the four terminals and a differential voltage (AC or DC), responsive to a magnetic field (AC or DC), is generated between the other two opposing ones of the four terminals
Data Source
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AI summary
An electronic circuit can be disposed upon a semiconductor substrate. An epitaxial layer can be disposed over the semiconductor substrate. The electronic circuit can include a Hall effect element, at least a portion of the Hall effect element disposed in the epitaxial layer. The electronic circuit can further include a current generator configured to generate a drive current that passes through the Hall effect element. The current generator can include a resistor disposed in the epitaxial layer and having characteristics such that a resistance of the resistor can vary with a stress of the semiconductor substrate, resulting in changes of the drive current, to compensate for variations in the sensitivity of the Hall effect element with the stress of the substrate.