TX Driver Switching for Fast Voltage Settling in Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Higher image sensor resolution in CMOS image sensors necessitates faster pixel readout, leading to increased signal noise due to increased frequency of pixel readout, which existing technologies have not adequately addressed.
Innovation Solution
The implementation of a TX driver powered by switches that alternately close and open to isolate external capacitances during data transfer, reducing voltage spikes and settling time, and controlling output voltage through multiple steps to achieve faster and less noisy data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel readout frequency is increased to achieve higher sensor resolution, then readout speed is improved, but signal noise increases
Solution Approach 1:
The patent segments the power supply voltage transition into multiple discrete steps (first voltage level, second voltage level, third voltage level) rather than a single direct transition. This segmentation allows the voltage to settle at each intermediate level, reducing noise propagation to the pixel array during high-frequency readout operations.
Solution Approach 2:
The patent performs preliminary voltage settling actions by transitioning through intermediate voltage levels before reaching the final operational voltage. This preliminary action allows capacitive loads to discharge and settle progressively, preventing noise spikes that would occur with direct voltage transitions during fast pixel readout.
2Speed
If voltage transitions are made faster to improve readout speed, then productivity is improved, but voltage spikes and settling time increase causing noise
Solution Approach 1:
The patent implements periodic voltage transitions through a multi-step sequence where the voltage alternates between different levels (first level, second level, third level) with settling periods at each stage. This periodic action allows the system to maintain fast overall transition while preventing harmful voltage spikes through controlled intermediate settling phases.
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 approach reduces noise levels and settling time, enabling faster and more accurate data transfer in CMOS image sensors, thereby improving image quality and reducing power consumption.
Implementation Method 1
a TX driver powered by switches that alternately close and open to isolate external capacitances during data transfer
Data Source
AI summary
Switching techniques for fast voltage settling in image sensors are described. In one embodiment, a transfer gate (TX) driver circuit of an image sensor includes a TX driver configured to provide a TX driver voltage to a plurality of pixels of an image sensor. A power supply (NVDD) is operationally coupled to the TX driver. A first switch (SW1) operationally coupling an outside capacitance (Cext) and the TX driver. A second switch (SW2) operationally coupling the Cext and the NVDD. A third switch (SW3) operationally coupling the NVDD and the TX driver. A falling edge of the TX driver voltage is configured to control a start of data transfer from individual pixels of the plurality of pixels. The SW1 and the SW2 are configured in an open position before the falling edge of the TX driver voltage. The SW3 is configured in a closed position before the falling edge.