Comparator Output Stabilization for High-Speed Image Sensing
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Solution Overview
Problem
Existing comparators face challenges in achieving high-speed operation while maintaining stability due to offset mismatches and reduced speed from auto-zero technology, leading to potential malfunctions.
Innovation Solution
A comparison circuit design that includes a comparator with a stabilization circuit, utilizing auto-zeroing and dominant pole compensation techniques to initialize and stabilize output nodes, allowing high-speed operation by disconnecting the stabilization circuit during comparison periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auto-zero technology is used to offset mismatches and offsets in the comparator, then the stability of the comparator is improved, but the operation speed of the comparator is reduced
Solution Approach 1:
The patent applies dynamics by making the stabilization circuit selectively connectable and disconnectable from the output node based on operational phase. During the auto-zero phase, the stabilization circuit is connected to provide stability and offset cancellation. During the comparison phase, the stabilization circuit is disconnected to enable high-speed operation. This dynamic switching resolves the contradiction between stability and speed by optimizing the circuit configuration for each operational phase.
Solution Approach 2:
The patent implements periodic action through the phased operation of the comparator circuit. The circuit alternates between an auto-zero phase (where the stabilization circuit is active and connected) and a comparison phase (where the stabilization circuit is inactive and disconnected). This periodic switching allows the circuit to achieve both stability during auto-zeroing and high speed during comparison, resolving the technical contradiction between these two requirements.
2Reliability
If various circuit components are added to the comparator to secure stability, then the offset cancellation capability is improved, but the operation speed is reduced
Solution Approach 1:
The patent uses dynamics by implementing a stabilization circuit that can be dynamically connected and disconnected. The stabilization circuit includes switching elements that control the connection to the output node based on the operational phase. This dynamic approach allows the circuit to have additional components for stability when needed (during auto-zero phase) while maintaining simplicity and high speed when the stabilization circuit is disconnected (during comparison phase).
Solution Approach 2:
The patent applies preliminary action by performing offset cancellation and stabilization operations in advance during the auto-zero phase before the actual comparison operation. The stabilization circuit is activated beforehand to initialize the comparator and cancel offsets, ensuring that the comparison phase can proceed at high speed without being burdened by stability concerns. This preliminary stabilization action resolves the contradiction by separating the stability-enhancing operations from the speed-critical comparison operation.
Data Source
AI summary
A comparison circuit and an image sensing device including the same are disclosed. The comparison circuit includes a comparison block configured to include a comparator that compares signals of input nodes with each other within a first period and outputs a signal corresponding to a result of the comparison to an output node and configured to initialize the comparator by allowing a voltage of the output node to be fed back to an input terminal of the comparator within a second period, and a stabilization circuit configured to supply a first voltage to the output node within the second period. In the second period, the stabilization circuit is connected to the output node to supply the first voltage. In the first period, connection between the stabilization circuit and the output node is cut off.