Image Sensor Signal Transfer Circuit for Single-Line Differential Sensing
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Solution Overview
Problem
The increasing number of pixels in image sensors leads to a limit in operation frequency of data bus, which can be overcome by increasing bus channels, but this results in larger device sizes and reduced design margin due to the need for multiple signal lines for differential sensing.
Innovation Solution
A signal transfer circuit that converts single-ended signals to differential signals using a transmission circuit, conversion circuit, and sensing output circuit, allowing signal transfer through a single line without compromising performance, thereby reducing the number of signal lines and device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the number of bus channels is increased to overcome the operation frequency limit, then the operation frequency can be improved, but the size of the image sensor increases
Solution Approach 1:
The patent combines differential signaling capability into a single-ended signal transmission system. The conversion circuit generates complementary differential signals from a single-ended input signal, allowing differential sensing to be performed using only one signal line instead of requiring separate differential signal lines. This merging approach maintains high-speed operation while reducing the overall device size.
Solution Approach 2:
The single signal line is made multi-functional by enabling it to carry both single-ended transmission and differential sensing functions. The conversion circuit allows the same signal line to be used for both transmission and differential signal generation, eliminating the need for additional dedicated differential signal lines and thereby reducing device size while maintaining operation frequency.
2Reliability
If multiple signal lines are used for differential sensing, then signal transfer performance can be maintained, but the device size increases and design margin is reduced
Solution Approach 1:
The conversion circuit acts as an intermediary that transforms a single-ended signal into differential signals. This intermediary component enables differential sensing performance using only one signal line, maintaining signal transfer reliability while eliminating the need for multiple signal lines and reducing device size.
Solution Approach 2:
The system changes the signal parameter representation by converting from single-ended to differential signaling dynamically. The conversion circuit generates complementary signals with opposite swings from a single-ended input, allowing differential sensing to be performed with the same physical signal line, thus maintaining performance while reducing device size.
Data Source
AI summary
A signal transfer circuit includes a transmission circuit, a conversion circuit and a sensing output circuit. The transmission circuit outputs a driving signal to a signal line. The conversion circuit receives an input signal that is a single-ended signal transferred through the signal line and converts the input signal to a differential signal including a first output amplified signal and a second output amplified signal. The first output amplified signal swings downwardly from a first output DC level and the second output amplified signal swings upwardly from a second output DC level that is lower than the first output DC level. The sensing output circuit generates an output signal based on the differential signal. The number of the signal lines is reduced without decrease in performance of signal transfer, and sizes of the signal transfer circuit and the device including the signal transfer circuit are reduced.