Capacitance-to-Digital Converter Switching for Extended Range
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Solution Overview
Problem
MEMS capacitive sensors have a limited measurement range, which is exacerbated by sigma-delta based capacitance-to-digital converters that saturate when the sensing capacitor's capacitance equals the reference capacitor's capacitance, restricting their utility and increasing the size and cost of the converter.
Innovation Solution
The capacitance-to-digital converter dynamically switches or reverses the electrical connection between the sensing and reference capacitors upon saturation, effectively doubling the measurement range while maintaining high resolution and linearity, and allows for a reduction in the size of the reference capacitor, thereby reducing the size and cost of the converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the size of the reference capacitor is increased to extend the measurement range, then the measurement range is improved, but the size and cost of the converter increase
Solution Approach 1:
The patent applies dynamics by making the capacitor configuration adjustable through switching mechanisms. The system dynamically reconfigures the capacitor network between different operational modes (first configuration with first capacitor, second configuration with second capacitor) based on measurement requirements, allowing the measurement range to be extended without permanently increasing the physical size of the converter.
Solution Approach 2:
The patent implements multi-functionality by designing a single converter that can operate in multiple measurement modes using different capacitor configurations. The same hardware infrastructure supports both a first measurement mode using a first capacitor and a second measurement mode using a second capacitor, enabling the converter to handle both small and large capacitance measurements without requiring separate dedicated circuits for each range.
2Measurement precision
If sigma-delta based capacitance-to-digital converters are used, then high resolution and linearity are achieved, but the measurement range is limited by the reference capacitor size
Solution Approach 1:
The patent resolves this contradiction by dynamically switching between different capacitor configurations during operation. The system maintains high resolution and linearity through the sigma-delta modulation architecture while extending the measurement range by reconfiguring the capacitor network. The switching mechanism allows the system to adapt its capacitance ratio to match the measurement requirements, thereby expanding the usable range without sacrificing precision.
Solution Approach 2:
The patent changes the capacitance parameters by utilizing multiple capacitors with different values (first capacitor and second capacitor) and switching between them. This parameter variation allows the system to maintain optimal capacitance ratios for high-resolution measurements across different measurement ranges, effectively decoupling the resolution capability from the fixed reference capacitor size limitation.
3Adaptability or versatility
If parallel distributed measurement sensing with multiple readout circuits is implemented, then the measurement range is widened, but the complexity, cost, and size of the converter increase
Solution Approach 1:
The patent reduces complexity by implementing a single multi-functional readout circuit that can operate in multiple measurement modes. Instead of requiring separate parallel readout circuits for different measurement ranges, the invention uses one versatile circuit that switches between different capacitor configurations to handle various measurement scenarios, thereby achieving wide measurement range without proportionally increasing circuit complexity.
Solution Approach 2:
The patent merges multiple measurement functions into a single integrated converter design. By combining the first and second capacitor configurations within one converter and using a unified switching mechanism to select between them, the system achieves the functionality of multiple dedicated circuits while maintaining a single, more manageable hardware architecture, thus reducing overall complexity.
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 extends the measurement range of the converter, enabling it to handle broader value ranges with improved performance and reduced size and cost, while maintaining sensitivity and low power consumption.
Implementation Method 1
measuring a change in charge stored by the second capacitor. The change in charge is representative of a corresponding change in a value
Data Source
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AI summary
A capacitance-to-digital converter and an associated method and computer program product are provided that have an extended measurement range. A capacitance-to-digital converter includes first and second capacitors with the second capacitor being configured to measure a change in a value. The capacitance-to-digital converter also includes first and second switches switchably connecting the first and second capacitors, respectively, to a reference voltage while the first and second switches are in a first position such that charge is stored by the first and second capacitors in response to the reference voltage. The capacitance-to-digital converter further includes a saturation detector configured to detect the charge stored by the second capacitor equaling or exceeding the charge stored by the first capacitor and, in response, causing the first and second switches to switch to a second position while continuing to measure the change in the value with the charge stored by the second capacitor.