Column ADC ALU With Shared Gray Code for Correlated Multiple Sampling
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Solution Overview
Problem
Current image sensors face challenges in enhancing their functionality and performance metrics such as resolution and power consumption, particularly in analog to digital conversion processes, which affect their ability to accurately capture and process image data.
Innovation Solution
The implementation of a readout circuit with parallel column arithmetic logic units and a shared Gray code generator that performs correlated double sampling or multiple sampling operations, enabling efficient analog to digital conversion by generating digital representations of analog image signals through the difference between signal and black level samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel column arithmetic logic units with shared Gray code generator are implemented, then image data processing efficiency is enhanced, but device complexity increases
Solution Approach 1:
Multiple column ALUs share a common Gray code generator circuit, reducing the total number of identical circuits needed. The shared generator produces Gray code sequences that are distributed to multiple ALUs, achieving resource utilization optimization and lowering overall device complexity while maintaining parallel processing capability
Solution Approach 2:
The arithmetic logic unit is designed with multi-functional capability to perform various operations including correlated double sampling, correlated multiple sampling, analog-to-digital conversion, and different arithmetic operations (addition, subtraction, multiplication, division) through a single unified circuit structure, thereby improving processing efficiency without proportionally increasing device complexity
2Measurement precision
If correlated multiple sampling operations are performed, then signal-to-noise ratio is improved, but power consumption increases
Solution Approach 1:
The circuit performs sampling operations in periodic cycles, alternating between active sampling phases and idle/reset phases. During correlated multiple sampling, the circuit systematically cycles through multiple sample acquisitions followed by correlated processing, enabling noise reduction through periodic measurement while managing power consumption through controlled operational cycles
Solution Approach 2:
The pipeline architecture maintains continuous data flow through the system, with multiple stages processing different data simultaneously. This continuity allows the system to perform correlated multiple sampling operations efficiently without idle cycles, improving signal-to-noise ratio through sustained operational momentum while optimizing power utilization
3Measurement precision
If higher resolution image sensors are implemented, then image quality is improved, but power consumption increases
Solution Approach 1:
The system replaces complex high-resolution analog-to-digital conversion mechanisms with a simplified approach using Gray code-based sequential comparison. Instead of using high-power successive approximation converters, the invention uses a sequence of comparators that incrementally determine digital values through Gray code transitions, reducing power consumption while maintaining high conversion precision for high-resolution imaging
Data Source
AI summary
An arithmetic logic unit (ALU) includes a front end latch stage coupled to latch Gray code (GC) outputs of a GC generator in response to a comparator output. A signal latch stage is coupled to latch outputs of the front end latch stage. A GC to binary stage is coupled to generate a binary representation of the GC outputs latched in the signal latch stage. First inputs of an adder stage are coupled to receive outputs of the GC to binary stage. Outputs of the adder stage are generated in response to the first inputs and second inputs of the adder stage. A pre-latch stage is coupled to latch outputs of the adder stage. A feedback latch stage is coupled to latch outputs of the pre-latch stage. The second inputs of the adder stage are coupled to receive outputs of the feedback latch stage.