Compensated Capacitor Layout for ADC Nonlinearity Reduction
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Solution Overview
Problem
Capacitor voltage dependence leads to nonlinearity in electronic systems, which can limit the performance of components like analog-to-digital converters (ADCs) by introducing common-mode rejection ratio (CMRR) limitations.
Innovation Solution
A system using capacitors with different physical spacings and a compensation circuit to offset voltage-dependent signal contributions, reducing nonlinearity without increasing capacitor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitor plate spacing is increased to decrease voltage coefficient, then voltage dependence is reduced, but capacitor size increases
Solution Approach 1:
The patent divides the capacitor system into multiple separate capacitors (first capacitor and second capacitor) with different physical spacings. By segmenting the single capacitor function into multiple components, the system can combine their effects to achieve voltage independence without requiring any single capacitor to have large plate spacing, thus avoiding increased size.
Solution Approach 2:
The patent uses the voltage-dependent effect of one capacitor to counterbalance the voltage-dependent effect of another capacitor. The first capacitor with larger plate spacing has reduced voltage coefficient, while the second capacitor with smaller plate spacing has higher voltage coefficient. When combined in the compensation circuit, these opposite effects cancel out, achieving voltage independence without requiring either capacitor to be oversized.
2Manufacturing precision
If capacitor size is increased to reduce voltage coefficient, then nonlinearity is reduced, but device area increases
Solution Approach 1:
The patent segments the capacitance function into multiple smaller capacitors with different physical characteristics. Instead of using one large capacitor to reduce nonlinearity, the system uses multiple smaller capacitors whose combined effect achieves the desired nonlinearity reduction, thereby reducing the total device area required.
Solution Approach 2:
The patent changes the physical parameters (plate spacing) of the capacitors to create different voltage coefficients. By selecting capacitors with specific spacing values, the system optimizes the voltage dependence characteristics without requiring large physical dimensions, thus reducing device area while maintaining manufacturing precision.
3Measurement precision
If ADC common-mode rejection ratio is improved, then measurement accuracy is improved, but capacitor nonlinearity limits CMRR
Solution Approach 1:
The patent applies counterbalancing by using two capacitors with opposite voltage-dependent characteristics. The first capacitor's voltage dependence compensates for the second capacitor's voltage dependence, creating an overall voltage-independent system. This enables the ADC to achieve high common-mode rejection ratio and measurement accuracy without being limited by capacitor nonlinearity.
Solution Approach 2:
The compensation circuit uses feedback principles by continuously monitoring and counteracting the voltage-dependent effects. The circuit is configured to detect voltage changes and use the complementary capacitor to provide opposing effects, thereby maintaining measurement accuracy and CMRR across varying voltage conditions.
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 system effectively minimizes voltage-dependent effects in capacitors, enhancing the accuracy of ADCs by improving CMRR and reducing nonlinearity in electronic circuits.
Implementation Method 1
A capacitor may have a capacitance value that is expressed in terms of the ratio of charge stored to voltage across the capacitor. The capacitance value of a capacitor may change depending upon the voltage across the capacitor.
Implementation Method 2
The nonlinearity may be due to a voltage dependent property of the dielectric.
Data Source
AI summary
A system for reducing a voltage-dependent effect of a first capacitor caused by a first voltage may include the first capacitor, which may include a first physical spacing between a first capacitor terminal conductor of the first capacitor and a second capacitor terminal conductor of the first capacitor. The system may also include a second capacitor, which may include a second physical spacing between a first capacitor terminal conductor of the second capacitor and a second capacitor terminal conductor of the second capacitor, where the second physical spacing is different from the first physical spacing. The system may also include a compensation circuit, which may be arranged to receive and at least partially offset a voltage dependent signal contribution from each of the first and second capacitors for output to a signal-processing circuit.