Image Sensor Comparator Circuit for Low-Power Accurate AD Conversion
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Solution Overview
Problem
Conventional analog-to-digital converters (ADCs) in image sensors face high power consumption and introduce undesirable distortions due to comparator artifacts, particularly during inversion operations.
Innovation Solution
The implementation of a comparator configuration in an image sensor that includes specific capacitor and transistor arrangements to reduce power consumption and minimize signal distortions, featuring a difference amplifier with capacitors and transistors connected in specific configurations to manage the comparison of pixel and reference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional ADC comparators are used to perform analog-to-digital conversion, then the conversion function is achieved, but power consumption becomes excessively large
Solution Approach 1:
The comparator is divided into two operational modes: a first comparison mode for normal operation and a second comparison mode for inversion operations. This segmentation allows the circuit to optimize power consumption by selectively activating different operational modes based on the specific conversion requirements, thereby reducing overall power consumption while maintaining conversion accuracy.
Solution Approach 2:
The comparator dynamically switches between different operational modes (first comparison mode and second comparison mode) depending on the conversion requirements. This dynamic adaptation enables the circuit to adjust its behavior to minimize power consumption during inversion operations while preserving the necessary conversion function and accuracy.
2Reliability
If conventional ADC comparators are used to perform comparison operations, then the conversion is completed, but undesirable distortions and artifacts are introduced in the output signals
Solution Approach 1:
The comparison operation is segmented into distinct modes: a first comparison mode for standard operations and a second comparison mode specifically designed to handle inversion operations without introducing artifacts. This segmentation eliminates signal distortions by ensuring that inversion operations are performed in a controlled manner that prevents the generation of unwanted artifacts in the output signal.
Solution Approach 2:
The comparator circuit introduces an intermediate operational state through the second comparison mode, which acts as a mediator to handle inversion operations. This intermediate mode ensures that inversion operations are performed in a controlled manner that prevents the generation of unwanted artifacts in the output signal, thereby improving signal quality.
Data Source
AI summary
Provided is an image sensor including: a pixel section configured to include a plurality of pixels arranged therein; and an AD conversion unit configured to perform analog-to-digital (AD) conversion on a pixel signal on the basis of a result of comparison between a first voltage of a signal, which is obtained by adding, via capacitances, the pixel signal of the pixel and a reference signal that linearly changes in a direction opposite to the pixel signal, with a second voltage serving as a reference.