Line Sensor ADC Sharing With Analog Memory for Low-Area Readout
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Solution Overview
Problem
Existing photoelectric conversion devices require a number of ADCs equal to the number of pixels that simultaneously output analog voltage signals, leading to increased area and power consumption, as well as potential issues with crosstalk and gradations in color and brightness in captured images.
Innovation Solution
A photoelectric conversion device configuration where analog voltage signals from N pixels are temporarily stored in an analog memory and converted using N−1 or fewer ADCs, reducing the number of ADCs needed and minimizing differences in signal output timing between pixels to prevent gradations, while also optimizing ADC placement to reduce parasitic resistance and stray capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of ADCs is equal to the number of pixels that simultaneously output analog voltage signals, then each pixel signal can be converted independently, but the area and power consumption of the device increase
Solution Approach 1:
Multiple ADCs are merged into a single shared ADC that sequentially converts analog signals from multiple pixels. The analog memory buffers the analog voltage signals from N pixels, allowing one ADC to service all N pixels by sequentially reading and converting each signal, thereby reducing the total number of ADCs from N to 1 while maintaining conversion capability for all pixels
Solution Approach 2:
A single ADC is designed to perform multiple conversion functions by sequentially processing analog signals from different pixels. The ADC serves as a universal converter that can handle signals from any of the N pixels by reading them from the analog memory in sequence, making one component perform the work of N dedicated ADCs
2Measurement precision
If the number of ADCs is equal to the number of pixels that simultaneously output analog voltage signals, then each pixel signal can be converted independently, but power consumption increases
Solution Approach 1:
Multiple power-consuming ADC units are merged into a single ADC unit that shares the conversion function across all pixels. By consolidating N ADCs into one, the total power consumption is reduced proportionally since only one ADC circuit is actively converting signals at any given time, while the analog memory maintains the signals for sequential processing
Solution Approach 2:
The single ADC operates in a periodic sequential manner, dedicating specific time slots to convert signals from different pixels. Instead of N ADCs operating simultaneously and continuously consuming power, one ADC operates periodically through each pixel's signal in sequence, reducing overall power consumption while completing the same total conversion task
3Productivity
If multiple ADCs are used for simultaneous A/D conversion, then conversion speed is high, but the number of components and device complexity increase
Solution Approach 1:
Multiple ADC components are merged into a single ADC component that achieves equivalent total conversion throughput by sequential processing. The analog memory enables this merging by buffering all analog signals simultaneously, allowing one ADC to service multiple pixels without bottlenecking the overall conversion speed
Solution Approach 2:
The analog memory performs preliminary storage of all analog voltage signals from N pixels before conversion. By pre-buffering all signals in analog form, the system enables a single ADC to sequentially convert each signal without waiting for new signals to arrive, maintaining high conversion throughput while using fewer components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the area and power consumption of the photoelectric conversion device, enhances conversion speed, and minimizes color and brightness gradations in images by allowing simultaneous A/D conversion of signals from multiple pixels with fewer ADCs, improving overall efficiency and image quality.
Implementation Method 1
a plurality of pixels configured to output analog voltage signals in response to incident light
Data Source
AI summary
A photoelectric conversion device includes a plurality of pixels configured to output analog voltage signals in response to incident light; an analog memory configured to store the analog voltage signals output from the plurality of pixels; and an analog/digital (A/D) converter configured to perform A/D conversion on the analog voltage signal from the analog memory. The plurality of pixels includes N pixels configured to simultaneously output analog voltage signals to the analog memory. The A/D converter includes (N−1) or less A/D converters configured to perform A/D conversion on the analog voltage signals that have been simultaneously output from the N pixels and stored in the analog memory.