Magnetic Sensor Readout Circuit Linearization via Segmented ADC
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Solution Overview
Problem
Current digital magnetic field sensors, particularly fluxgate magnetometers, face challenges with high power consumption, large size, and slow throughput due to the need for high precision analog blocks and filtering in signal acquisition electronics, which limits their performance in mobile and navigation applications.
Innovation Solution
A read-out circuit that partitions analog-to-digital conversion into a fast conversion process for calculating most significant bits and a delta-sigma based conversion process for calculating least significant bits, allowing for efficient generation of a compensation signal to linearize the sensor output, reducing latency and power consumption while increasing resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision analog blocks and filtering are used in signal acquisition electronics, then measurement precision is improved, but power consumption increases and device size increases
Solution Approach 1:
The patent segments the analog-to-digital conversion process into two distinct stages: a fast conversion process that calculates the most significant bits and generates the compensation signal, and a delta-sigma based conversion process that calculates the least significant bits. This segmentation allows each stage to be optimized independently, reducing the need for high precision analog blocks throughout the entire conversion chain while maintaining overall measurement precision.
Solution Approach 2:
The patent extracts the compensation signal generation function from the main measurement path and implements it through the fast conversion process. By taking out this function and handling it separately with lower precision requirements, the main measurement path can use simpler, lower power analog blocks while the compensation signal is generated efficiently through digital processing.
2Measurement precision
If high precision analog blocks and filtering are used in signal acquisition electronics, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent segments the conversion process into fast and delta-sigma stages, allowing the use of simpler analog blocks in each stage rather than requiring high precision analog blocks throughout. This reduces the overall device area while maintaining measurement precision through the combination of both conversion stages.
Solution Approach 2:
The patent replaces complex analog filtering and high precision analog processing with a digital-based two-stage conversion approach. The fast conversion process provides coarse measurement and compensation signal generation, while the delta-sigma process refines the measurement digitally, reducing the need for large analog filtering circuits and high precision analog components.
3Productivity
If traditional single-stage analog-to-digital conversion is used, then device complexity is low, but throughput is slow and latency is high
Solution Approach 1:
The patent segments the conversion process into two parallel paths: a fast conversion path that quickly generates the compensation signal and most significant bits, and a delta-sigma conversion path that processes the least significant bits. This segmentation enables the system to operate at higher throughput by processing different bits at different speeds rather than requiring all bits to be processed at the same slow rate.
Solution Approach 2:
The fast conversion process performs preliminary conversion of the most significant bits and generates the compensation signal before the delta-sigma conversion process completes the least significant bits. This preliminary action allows the system to provide initial measurement results and compensation faster, reducing overall latency while the more complex delta-sigma process completes in the background.
4Measurement precision
If traditional single-stage analog-to-digital conversion is used, then device complexity is low, but measurement precision and resolution are limited
Solution Approach 1:
The patent segments the conversion into fast and delta-sigma stages, with each stage optimized for its specific function. The fast conversion provides coarse measurement with lower complexity, while the delta-sigma conversion refines the measurement to achieve high precision and resolution. This segmented approach achieves high measurement precision without requiring a single complex high-precision conversion stage.
Solution Approach 2:
The patent implements dynamic operation where the fast conversion process operates at higher speed for coarse measurement and compensation generation, while the delta-sigma conversion process operates at lower speed for fine measurement refinement. This dynamic approach allows the system to achieve high measurement precision by combining results from conversion stages operating at different speeds and precision 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
This approach enables lower power dissipation by 60-75% compared to prior art systems, reduces latency, and enhances throughput and resolution, making it suitable for mobile and navigation applications with improved measurement precision.
Implementation Method 1
A fluxgate magnetometer consists of a small, magnetically susceptible core wrapped by two coils of wire. An alternating electrical current is passed through one coil, driving the core through an alternating cycle of magnetic saturation; i.e., saturated, unsaturated, inversely saturated, unsaturated, saturated, and so forth.
Implementation Method 2
An alternating electrical current is passed through one coil, driving the core through an alternating cycle of magnetic saturation
Implementation Method 3
This constantly changing field induces an electrical voltage or EMF (electro-magnetic force) in the second coil
Implementation Method 4
a magnetic field is generated via a compensation current flowing through the loops of a sensor coil or an independent compensation coil to oppose the external magnetic field that the sensor sees
Data Source
AI summary
A method of processing an output signal and a readout circuit for a magnetic field sensor are disclosed. The purpose of the readout circuit is to generate a digital representation of the magnetic field vector strength. It comprises an input stage for receiving an output signal of the magnetic field sensor; an output stage for outputting a digital output signal corresponding to the sensor output signal; and an analog to digital conversion circuit. The analog to digital conversion circuit receives the sensor output signal and performs, in sequence, a fast conversion process for calculating a number of most significant bits of the digital output signal corresponding to the sensor output signal and for generating a compensation signal, and a delta sigma based conversion process for calculating at least one least significant bit of the digital output signal. The compensation signal is fed back to the sensor input for linearization. The delta sigma based conversion takes advantage of oversampling and noise shaping to increase resolution.