Magnetic Field Sensor Topology Using High-Speed Comparator
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Solution Overview
Problem
Magnetic field sensors face challenges in reducing circuit area while minimizing DC offset voltage, particularly in applications where compact designs are crucial and sampling jitter affects accuracy.
Innovation Solution
The proposed magnetic field sensor topology eliminates the sinc filter and employs a high-speed comparator to compare a processed magnetic field signal to a reference signal multiple times during a chopping period, reducing sampling jitter and achieving a smaller circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sinc filter is used to sample and average the magnetic field signal, then measurement precision is improved, but circuit area increases
Solution Approach 1:
The patent extracts and removes the sinc filter from the circuit topology, eliminating the need for this large-area component while maintaining signal processing functionality through alternative means (sampling and averaging implemented in firmware/software)
Solution Approach 2:
The patent replaces the hardware-based sinc filter with a software/firmware-based signal processing approach, where sampling and averaging are performed digitally rather than through analog filter circuitry, significantly reducing circuit area
2Measurement precision
If a high speed comparator is used to perform multiple comparisons within a chopping period, then sampling jitter is reduced, but device complexity increases
Solution Approach 1:
The patent employs periodic chopping action at a defined chopping frequency, where the comparator performs multiple comparisons within each chopping period. This periodic structure organizes the complex sampling process into manageable cycles, reducing jitter while maintaining systematic control
Solution Approach 2:
The patent changes the operational parameters of the comparator by enabling it to perform multiple comparisons within a single chopping period rather than a single comparison per period. This parameter change increases sampling density and reduces jitter without requiring fundamentally new circuitry
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 results in a more compact sensor design with reduced sampling jitter, enhancing accuracy and cost-effectiveness by eliminating the need for a sinc filter and utilizing a Schmitt trigger circuit for multiple comparisons within a chopping time period.
Implementation Method 1
Some sensors include one or magnetic field sensing elements, such as a Hall effect element or a magnetoresistive element, to sense a magnetic field
Data Source
AI summary
A magnetic field sensor includes a magnetic field sensing element to generate a magnetic field signal indicative of a sensed magnetic field, a modulator to modulate the magnetic field signal at a chopping frequency, a front end amplifier coupled to receive the magnetic field signal and generate an amplified signal, and a demodulator configured to demodulate the amplified signal at the chopping frequency. The sensor further includes a low pass filter to process the amplified signal and generate a low pass filtered signal and a Schmitt trigger circuit. The Schmitt trigger circuit includes a comparator having a first input coupled to receive the low pass filtered signal, a second input coupled to receive a reference signal, and an output at which a comparator output signal is provided. The comparator is configured to perform a plurality of comparisons within a chopping time period that is the inverse of the chopping frequency.