Capacitance Interface Circuit Segmentation for IC Integration
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Solution Overview
Problem
Existing capacitance interface circuits face challenges in designing a capacitor Cs that is much greater than Ci to accumulate similar charges during each period, making it difficult to integrate in an IC due to the large size requirement.
Innovation Solution
A capacitance interface circuit with a first external inductive capacitor divided into a variable and an invariable portion, using two feedback capacitors and a fully-differential amplifier, where the control unit generates control signals and a reset signal to cancel the invariable portion, allowing the charge converter to work only on the variable portion, increasing data processing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitance of capacitor Cs is designed to be much greater than that of capacitor Ci to accumulate similar charges during each period, then the charge accumulation accuracy is improved, but the capacitor size becomes too large to be integrated in an IC
Solution Approach 1:
The external inductive capacitor Cext is divided into a fixed portion Cfix and a variable portion Cvar. The fixed portion is cancelled by the cancellation means, allowing the charge converter to work only on the variable portion. This segmentation enables accurate charge measurement without requiring a large total capacitance, resolving the contradiction between measurement precision and capacitor size for IC integration.
Solution Approach 2:
The invention extracts and removes the fixed portion Cfix of the capacitor from the measurement process through the cancellation means. By taking out the unnecessary fixed capacitance component, the system achieves accurate charge accumulation measurements using only the variable portion, thereby avoiding the need for excessively large capacitors that would be required if the entire capacitance had to be used for measurement.
2Quantity of substance
If the capacitance of capacitor Cs is increased to accumulate sufficient charges, then the charge accumulation capability is improved, but the integration difficulty in IC increases
Solution Approach 1:
The cancellation means extracts and removes the fixed portion Cfix from the total capacitance, allowing the charge converter to operate only on the variable portion Cvar. This extraction enables sufficient charge accumulation capability to be achieved with a much smaller effective capacitance, making IC integration feasible without requiring excessively large capacitors.
Solution Approach 2:
The invention changes the effective capacitance parameter from the total capacitance (Cfix + Cvar) to only the variable portion Cvar by cancelling the fixed portion. This parameter change maintains the charge accumulation capability while dramatically reducing the physical capacitor size required, thereby enabling IC integration.
3Measurement precision
If a large capacitor Cs is used to ensure sufficient charge accumulation, then the measurement accuracy is improved, but the device complexity and area increase
Solution Approach 1:
The external inductive capacitor is segmented into fixed and variable portions, with the fixed portion being cancelled out. This segmentation allows the measurement system to achieve high precision using only the variable portion, thereby maintaining measurement accuracy while reducing the required circuit area compared to using a single large capacitor.
Solution Approach 2:
The fixed portion of the capacitor is extracted and removed from the measurement process through the cancellation means. This extraction allows the system to achieve accurate capacitance measurements with a much smaller effective capacitance, thereby reducing the overall circuit area required while maintaining measurement precision.
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 design allows for accurate and efficient charge accumulation by the feedback capacitors, ensuring similar charge accumulation during each period, and enables the capacitance interface circuit to be integrated in an IC without the need for excessively large capacitors.
Implementation Method 1
the capacitor Ci is charged. Next, charges stored in the capacitor Ci are conducted/transferred into the capacitor Cs through charge pump means
Data Source
AI summary
A capacitance interface circuit is provided. An external inductive capacitor is divided into a variable portion and an invariable portion. The capacitance of an internal adjustable capacitor is designed to be equal or close to the fixed capacitance of the external inductive capacitor. The internal adjustable capacitor is used for storing charges having a polarity opposite to that of the invariable portion of the external inductive capacitor in order to neutralize the effect of the invariable portion of the external inductive capacitor. Thus, a charge converter composed of a fully-differential amplifier and feedback capacitors needs only work on the variable portion of the external inductive capacitor, and accordingly the accuracy in subsequent data processing is increased.