Column A/D Converter Power Isolation for Low-Noise Imaging
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Solution Overview
Problem
Power supply voltage fluctuations negatively impact the A/D conversion operation in column-type A/D converters used in solid-state image sensors, leading to noise in digital images.
Innovation Solution
The A/D converter employs a separate power supply line for the arithmetic unit that is not affected by voltage fluctuations, using N and P channel-type MOSFETs and stabilized voltage sources to maintain a stable power supply, and a similar approach for the ground voltage line to prevent fluctuations from affecting the A/D conversion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common power supply line is used for the arithmetic unit and other circuits, then the device complexity is reduced, but the A/D conversion precision deteriorates due to power supply voltage fluctuations
Solution Approach 1:
The power supply system is segmented into a common power supply line for general circuits and a dedicated separate power supply line for the arithmetic unit. This segmentation isolates the arithmetic unit from voltage fluctuations affecting other circuits, thereby maintaining A/D conversion precision while managing device complexity through structured power distribution.
2Measurement precision
If a separate power supply line is provided for the arithmetic unit, then the A/D conversion precision is improved, but the device complexity increases
Solution Approach 1:
The power supply system is segmented into a common power supply line for general circuits and a dedicated separate power supply line for the arithmetic unit. This segmentation isolates the arithmetic unit from voltage fluctuations affecting other circuits, thereby maintaining A/D conversion precision while managing device complexity through structured power distribution.
3Ease of operation
If power supply voltage fluctuates, then the ease of operation is maintained, but the A/D conversion reliability deteriorates due to noise in digital images
Solution Approach 1:
The power supply system is segmented into a common power supply line for general circuits and a dedicated separate power supply line for the arithmetic unit. This segmentation isolates the arithmetic unit from voltage fluctuations affecting other circuits, thereby maintaining A/D conversion precision while managing device complexity through structured power distribution.
Data Source
AI summary
An A/D converter compares one or more analog voltages to be converted with a reference voltage given by a voltage change value of ramp voltage whose voltage value changes monotonically for a certain period or a voltage proportional to the voltage change value, converts each analog voltage to a digital value corresponding to the reference voltage, and outputs it, the A/D converter comprising an arithmetic unit for comparison between the analog voltage and reference voltage with respect to each analog voltage, the arithmetic unit having a first power supply line for receiving a power supply voltage, wherein the first power supply line is provided as another power supply line not affected by voltage fluctuation of a second power supply line for supplying a system power supply voltage by providing a MOS transistor whose gate terminal is connected to a stabilized voltage source between the first and second power supply lines.