Pixel Control Signal Driver Adaptive Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face issues with uniform pixel response and noise due to high resistance in control signal lines, leading to horizontal noise in captured images.
Innovation Solution
A pixel control circuit with adaptive bandwidth is introduced, featuring a variable resistance circuit that adjusts series resistance to match the time constant of control signal lines, ensuring uniform rise and fall times across the pixel array and reducing noise during sampling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If high resistance control signal lines are used to connect pixel circuits, then the pixel array can be laid out with larger spacing between circuits, but horizontal noise increases and pixel response uniformity deteriorates
Solution Approach 1:
A buffer circuit is introduced as an intermediary between the control signal source and the pixel circuits. The buffer circuit has a low output impedance that drives the high-resistance control signal lines, thereby maintaining signal integrity and reducing noise while allowing larger pixel spacing.
Solution Approach 2:
The impedance characteristics of the control signal line are modified by introducing the buffer circuit, which changes the effective source impedance from high to low. This parameter change allows the line to drive larger capacitive loads with less noise and maintains uniform signal distribution across the pixel array.
2Device complexity
If high resistance control signal lines are used, then routing complexity is reduced, but pixel response uniformity across columns deteriorates
Solution Approach 1:
The buffer circuit serves as a mediator that actively compensates for the high resistance of the control signal lines. By providing strong driving capability, it ensures that all pixel circuits along a column receive uniform control signals with consistent rise and fall times, maintaining pixel response uniformity while allowing simple routing.
3Manufacturing precision
If control signal line resistance is increased, then manufacturing precision requirements are relaxed, but noise during sampling operations increases
Solution Approach 1:
The buffer circuit is positioned as an intermediary that isolates the pixel circuit array from the high-resistance control signal lines. The buffer's low output impedance compensates for the line resistance, reducing noise during sampling operations while allowing relaxed manufacturing precision for the control signal lines.
Data Source
AI summary
A pixel control circuit includes a first supply rail coupled to provide a first supply voltage. A second supply rail is coupled to provide a second supply voltage. A variable resistance circuit is coupled to the second power supply rail. A plurality of driver circuits is coupled between the first supply rail and the variable resistance circuit. Each one of the plurality of driver circuits is coupled to provide a control signal coupled to control a pixel circuit. The variable resistance circuit is coupled to provide a first resistance between the plurality of driver circuits and the second supply rail during a sampling operation of the pixel circuit. The variable resistance circuit is coupled to provide a second resistance between the plurality of driver circuits and the second supply rail during a non-sampling operation of the pixel circuit.