Pixel Data Line Readout Circuit for IR-Drop Reduction
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Solution Overview
Problem
Image sensors experience significant IR-drop phenomena due to resistance in signal lines between pixel output terminals and amplifier input terminals, leading to voltage drops that affect data accuracy.
Innovation Solution
The electronic device design includes a substrate with pixels and data lines, where the amplifier and current source are coupled to data lines, and a portion of the data line forms a conduction path, allowing a first current to flow to the amplifier and a second current to flow to the current source, minimizing voltage drops by optimizing current paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the signal line resistance is reduced to minimize IR-drop, then voltage accuracy is improved, but the signal line length or area must be reduced which may affect circuit layout flexibility
Solution Approach 1:
The patent segments the signal line into multiple sections by introducing intermediate buffer stages (such as source follower circuits) between the pixel output and the final amplifier. This segmentation allows the total signal line length to be extended without proportionally increasing the total resistance, as each segment is buffered to restore signal levels, thereby reducing the overall IR-drop effect while maintaining layout flexibility.
Solution Approach 2:
The patent introduces intermediary buffer circuits (source followers) that act as mediators between the pixel output node and the amplifier input. These intermediary stages provide current buffering and voltage restoration, effectively decoupling the high-impedance pixel output from the amplifier input and minimizing the impact of signal line resistance on voltage accuracy.
2Quantity of substance
If the signal line length is increased to accommodate more pixels, then pixel coverage is improved, but the IR-drop phenomenon worsens due to increased resistance
Solution Approach 1:
By segmenting the readout circuit into multiple columns, each with its own amplifier and buffer stage, the patent enables extended pixel array coverage without proportionally increasing the signal line resistance. Each column operates as an independent segment with restored signal levels, allowing the total number of pixels to be increased while maintaining voltage accuracy through periodic signal restoration at each segment boundary.
Solution Approach 2:
The patent transitions from a single-ended readout architecture to a differential readout architecture, adding a second dimension (the differential pair) to the signal path. This dimensional change allows the signal to be transmitted through longer lines with reduced vulnerability to IR-drop, as the differential configuration rejects common-mode voltage drops and allows for longer signal lines without proportional increases in voltage loss.
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 IR-drop, enabling the output data voltage from pixels to be transferred to the amplifier without significant voltage loss, thereby improving data accuracy and reducing signal degradation.
Implementation Method 1
at least a portion of the one of data lines forms a conduction path
Implementation Method 2
there is a resistance of the signal line between the output terminal of the pixel and the input terminal of the amplifier. As a result, the output data voltage of the pixel will suffer a serious voltage drop (IR-drop)
Data Source
AI summary
An electronic device is provided. The electronic device includes: a substrate, a plurality of pixels, a plurality of data lines, an amplifier and a current source. The pixels and data lines are disposed on the substrate. The amplifier and the current source are coupled to one of the data lines, wherein at least a portion of the one of data lines forms a conduction path. One of the pixels is coupled to the one of the data lines at a first node, and the first node is on the first conduction path. A first current that flows from the first node to the first source terminal is different from a second current that flows from the first node to the first output terminal.