Ramp Voltage Correction for Image Sensors
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Solution Overview
Problem
Image sensing devices face challenges in minimizing the settling time of ramp voltage and maintaining it constant across varying analog gains, leading to inefficiencies in analog-to-digital conversion processes.
Innovation Solution
The implementation of a ramp voltage generation and correction block system that adjusts ramp voltage based on bias signals and control signals, using a combination of driving units, switching units, and resistance elements to control the slope and settling time of the ramp voltage, ensuring stable detection of pixel signal voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ramp voltage slope is adjusted to control analog gain, then the analog gain can be optimized for different light intensities, but the settling time of the ramp voltage increases
Solution Approach 1:
The patent divides the single ramp voltage generation into two separate blocks: a ramp voltage generation block that produces the base ramp voltage, and a ramp voltage correction block that adjusts the slope. This segmentation allows independent optimization of gain control and settling time without mutual interference.
Solution Approach 2:
The ramp voltage correction block acts as an intermediary between the ramp voltage generation block and the detection block. It receives the base ramp voltage, applies slope correction based on control signals, and outputs the corrected ramp voltage, thereby mediating the trade-off between gain adaptability and settling time.
2Device complexity
If a conventional ramp voltage generation circuit is used, then the device complexity is reduced, but the settling time cannot be minimized and controlled across varying analog gains
Solution Approach 1:
The patent introduces dynamic control capabilities by adding control signals that adjust the ramp voltage slope in real-time. The correction block dynamically modifies the ramp voltage characteristics based on operating conditions, enabling settling time optimization across different analog gain settings without requiring completely different circuit structures.
Solution Approach 2:
The patent changes the slope parameter of the ramp voltage through the correction block. By adjusting the slope parameter dynamically based on control signals, the system can optimize settling time for different analog gain values without fundamentally changing the circuit architecture, thus maintaining relatively low device complexity.
3Productivity
If the ramp voltage falls by a predetermined voltage level in each clock cycle, then the analog-to-digital conversion can proceed, but the settling time is lengthened particularly in coarse ramp voltage
Solution Approach 1:
The correction block performs preliminary slope adjustment on the ramp voltage before it is used in the analog-to-digital conversion process. By pre-correcting the slope to optimal values based on control signals, the system ensures that the subsequent conversion process can proceed efficiently with minimized settling time, rather than dealing with suboptimal ramp characteristics during conversion.
Data Source
AI summary
An image sensing device includes a ramp voltage generation block suitable for generating a ramp voltage adjusted by a predetermined voltage in each predetermined cycle, based on a bias signal and a plurality of first ramp control signals; and a ramp voltage correction block suitable for correcting the ramp voltage in each predetermined cycle based on the bias signal and at least one second ramp control signal.