Charge-Domain Sigma-Delta ADC for Direct Sensor Coupling
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Solution Overview
Problem
Conventional oversampling converters rely on transistors, which limit their ability to directly couple with charge-based devices like image sensors, leading to suboptimal signal-to-noise ratios and power consumption in analog signal conversion tasks.
Innovation Solution
Implementing oversampling converters using charge domain components, such as charge coupled combiners, shift registers, and quantizers, which allow direct coupling with charge-based devices, improved signal-to-noise ratios, and reduced power consumption by using notch transfer gates and two capacitor charge multipliers to program charge addition or subtraction based on quantizer outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transistor-based implementations are used for oversampling converters, then the conversion functionality is achieved, but the signal-to-noise ratio is suboptimal and power consumption is high
Solution Approach 1:
The patent replaces transistor-based analog signal processing with charge domain components including charge coupled combiners, charge domain shift registers, and charge domain quantizers. This substitution eliminates the need for transistor switching operations and enables direct coupling with charge-based devices, thereby improving signal-to-noise ratio and reducing power consumption through more efficient charge transfer mechanisms
2Adaptability or versatility
If transistor-based implementations are used for oversampling converters, then the conversion functionality is achieved, but direct coupling with charge-based devices is limited
Solution Approach 1:
The patent employs charge domain components throughout the oversampling converter architecture, creating a homogeneous charge-based system that can directly interface with charge-output devices such as image sensors. This homogeneity eliminates the need for complex transistor-based interface circuits and enables straightforward direct coupling between the sensor and converter
3Measurement precision
If charge domain components are used, then direct coupling with charge-based devices is enabled and signal-to-noise ratio is improved, but the device structure becomes more complex
Solution Approach 1:
The charge domain components serve multiple functions within the system. The charge coupled combiner performs both signal summation and charge transfer, the charge domain shift register handles both signal delay and charge storage, and the charge domain quantizer performs both quantization and digital output generation. This multi-functionality reduces the overall device structure complexity despite using specialized charge domain components
Data Source
AI summary
A charge domain sigma delta analog to digital converter (ADC) is taught. A combiner is taught which acts as a delta operator and the same structure is also separately used as an adder in an NTF. The charge coupled combiner has a source of an input charge from a wired pair of diodes which creates a replica charge which cannot be destroyed. An output charge domain shift register comprised of memory nodes is provided. A second charge domain shift register and wired device is provided which is used with said combiner to implement an NTF. A quantizer is taught using a barrier whose height represents a discrete charge threshold. An NTF coupled to the quantizer provides charge which will either exceed or not exceed said threshold. A thyristor will actuate a subtract or add function at the delta combiner depending on the quantizer level to act as the DAC function of the ADC.