Column ADC Test Signal Selection for Interference Evaluation
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Solution Overview
Problem
In imaging devices with a large number of pixels, interference between column Analog-to-Digital Conversion (ADC) circuits occurs due to shared power supply noise, which cannot be sufficiently evaluated using existing methods that only select a ground voltage as a test signal.
Innovation Solution
A semiconductor device with conversion signal selection circuits that select between pixel output signals and test signals with varying test voltages for each ADC circuit, allowing for comprehensive evaluation of interference between column ADCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a ground voltage is used as a test signal to evaluate column ADC interference, then the evaluation method is simple, but the interference between column ADCs cannot be sufficiently evaluated
Solution Approach 1:
The patent applies parameter changes by varying the test voltage levels (using multiple voltage levels such as 0V, 0.5V, 1.0V, 1.5V, and 2.0V) instead of using a fixed ground voltage. This allows the evaluation to capture interference effects under different voltage conditions, thereby improving measurement precision while maintaining evaluation simplicity through automated multi-level testing.
2Measurement precision
If the number of pixels is increased to improve image quality, then the image quality improves, but interference between column ADCs increases
Solution Approach 1:
The patent applies preliminary action by conducting interference evaluation before the imaging device is deployed for actual imaging operations. The test signals are injected into column ADCs under controlled conditions to identify and characterize interference patterns in advance. This allows for compensation algorithms or design adjustments to be made before actual imaging, ensuring high image quality even with many pixels.
Solution Approach 2:
The patent replaces physical imaging operations with electrical test signal injections to evaluate interference. Instead of using actual optical inputs and complex imaging processes, the invention uses electrical test signals with varying voltage levels to directly stimulate column ADCs and measure interference effects, simplifying the evaluation while improving accuracy.
3Device complexity
If common power supply lines are used for column ADCs to reduce circuit complexity, then device complexity is reduced, but power supply noise causes varying interference
Solution Approach 1:
The patent introduces test signals as an intermediary to evaluate the effect of power supply noise on column ADCs. By injecting known test voltages through the common power supply line, the invention can characterize how power supply variations affect ADC performance. This intermediary approach allows for noise modeling and compensation without requiring separate power supply lines for each ADC, thus maintaining circuit simplicity while accounting for noise effects.
Data Source
AI summary
In semiconductor devices according to related art, it is impossible to sufficiently evaluate column ADC interference. According to one embodiment, a semiconductor device includes a plurality of analog/digital conversion circuits that are arranged in a column direction of a pixel array and convert a pixel output signal output from the pixel array for each row into a digital value, and a conversion signal selection circuit that selects one of the pixel output signal and a test signal having a test voltage for each analog/digital conversion circuit according to a test pattern and outputs the selected signal.