Sample and Hold Leakage Compensation via Segmented Capacitors
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Solution Overview
Problem
Leakage current in sample and hold circuits on integrated circuits causes charge buildup or depletion over time, leading to inaccurate representation of initially sampled values, and existing solutions either increase costs or size by enhancing capacitance or design, which are not optimal.
Innovation Solution
A sample and hold circuit design that models leakage current using a second switch and capacitor to compensate for the leakage across the primary switch, allowing for accurate retention of sampled values by subtracting the accumulated charge from the offset circuit, thereby maintaining the initial value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitance of the storage capacitor is increased to reduce the effect of leakage current, then the accuracy of stored value is improved, but the size and cost of the integrated circuit increase
Solution Approach 1:
The patent divides the storage system into two separate capacitors: a main storage capacitor (first capacitor) and a leakage compensation capacitor (second capacitor). The first capacitor holds the sampled value while the second capacitor captures and stores the leakage charge separately. This segmentation allows the main capacitor to be smaller while maintaining accuracy through the compensating action of the second capacitor.
Solution Approach 2:
The patent introduces a switching mechanism that acts as an intermediary to manage charge distribution between capacitors. The switch selectively connects and disconnects the capacitors, enabling the system to transfer leakage charge from the first capacitor to the second capacitor, thereby compensating for leakage effects without requiring a large main capacitor.
2Measurement precision
If the design of the storage capacitor is improved to reduce leakage current effects, then the accuracy of stored value is improved, but the manufacturing cost increases
Solution Approach 1:
Instead of designing a single complex high-performance capacitor, the patent segments the function into two simpler capacitors working together. This approach uses standard capacitor designs that are easier and cheaper to manufacture, while achieving the same accuracy goal through the dual-capacitor leakage compensation mechanism.
Solution Approach 2:
The patent creates a simplified copy of the storage function using the second capacitor, which specifically handles leakage charge. This copy capacitor can be designed with standard parameters and manufacturing processes, reducing overall manufacturing complexity and cost while maintaining the required precision.
3Measurement precision
If a leakage compensating circuit is added to the sample and hold circuit, then the accuracy of stored value is improved, but the device complexity increases
Solution Approach 1:
The patent segments the leakage compensation function into a separate, dedicated circuit module using a second capacitor and associated switching elements. This modular segmentation isolates the compensation functionality from the main storage circuit, making the overall system more manageable and potentially easier to integrate despite the added components.
Solution Approach 2:
The leakage compensating circuit operates continuously during the hold period, automatically capturing and storing leakage charge as it occurs. This continuous operation eliminates the need for complex periodic correction algorithms or additional control logic, simplifying the overall device while maintaining high accuracy.
Data Source
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AI summary
A sample and hold circuit in one aspect includes first and second switches. The first switch can be coupled to receive an input signal and to sample the input signal using a first capacitor. A first leakage current flows between first and second conductive terminals of the first switch and accumulates as a first leakage charge in the first capacitor. A second leakage current flows between the first and second conductive terminals of the second switch and accumulates as a second leakage charge in the second capacitor. An offset circuit produces a compensated sampled value by subtracting a quantity from a signal developed in response to the held sampled signal and charge accumulated through the first switch, wherein the quantity is developed in response to the accumulated leakage charge in the second capacitor.