Terminal Circuit for Crosstalk Control in CMOS Image Sensors
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Solution Overview
Problem
In CMOS image sensors, the close arrangement of signal lines leads to increased resistance and capacitance between them, causing crosstalk and signal charge leakage, which existing methods struggle to control effectively without compromising light gathering or signal transition rates.
Innovation Solution
A solid-state imaging device with a terminal circuit connected to one end of the transfer signal line, securing it at a constant voltage before inputting signals to adjacent lines, reduces the resistance and capacitance between signal lines, thereby controlling crosstalk and maintaining signal transition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If signal lines are closely arranged to increase pixel density, then the number of pixels can be increased, but the resistance and capacitance between signal lines increase causing crosstalk
Solution Approach 1:
The terminal circuit performs preliminary action by securing the signal line at a constant voltage before the main signal is input to adjacent lines. This proactive voltage stabilization prevents crosstalk from occurring in the first place, rather than attempting to correct it after the fact. The terminal circuit is activated in advance to create a stable electrical environment for subsequent signal transmission.
Solution Approach 2:
The terminal circuit acts as an intermediary element between the driver circuit and the signal line. It mediates the electrical interaction by providing a constant voltage reference that isolates the signal line from voltage fluctuations caused by adjacent line switching. This intermediary structure enables closely arranged signal lines to coexist without significant crosstalk interference.
2Reliability
If the width of signal lines is increased to reduce resistance and capacitance, then crosstalk can be reduced, but light gathering to photodiodes is blocked
Solution Approach 1:
The terminal circuit provides localized voltage stabilization at specific positions along the signal line where crosstalk is most problematic. Rather than uniformly increasing signal line width across the entire pixel array, the solution applies electrical compensation only where needed - at the terminal end of signal lines adjacent to actively driven lines. This localized approach maintains optimal light gathering while providing crosstalk suppression where it matters most.
3Reliability
If driver circuit output impedance is reduced to control crosstalk, then signal line voltage stability improves, but the effect is insufficient due to high signal line resistance
Solution Approach 1:
The solution segments the voltage control function between the driver circuit and the terminal circuit. The driver circuit maintains its original output impedance characteristics, while the terminal circuit independently provides voltage stabilization at the signal line endpoint. This segmentation allows each circuit to operate within its optimal parameters without requiring complex impedance matching or high-current drive capabilities.
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 effectively inhibits crosstalk and signal charge leakage, allowing for high-definition image capture by ensuring accurate signal transmission and reducing erroneous signals from adjacent lines.
Implementation Method 1
the resistance R increases at a portion distant from a driver circuit 102, and the capacitance C also increases between the signal lines 100 and 101
Implementation Method 2
the resistance R increases at a portion distant from a driver circuit 102, and the capacitance C also increases between the signal lines 100 and 101
Implementation Method 3
a photoelectric conversion portion for converting incident light into an electric signal and accumulating signal charge
Data Source
AI summary
A solid-state imaging device including a photoelectric conversion portion photoelectrically converting incident light into signal charge and accumulate the signal charge, a plurality of signal lines including a transfer signal line to which a transfer signal for reading the signal charge accumulated in the photoelectric conversion portion to a floating diffusion region is input, a driver circuit inputting a plurality of desired signals into the plurality of signal lines including the transfer signal line, and a terminal circuit connected to a side opposite to a side of the transfer signal line where the driver circuit is connected and to which a control signal for securing the transfer signal line at a constant voltage is input before a desired signal of the plurality of desired signals with respect to a signal line adjacent to the transfer signal line of the plurality of signal lines is input to the signal line adjacent to the transfer signal line.