Column Memory Repair Circuitry for Image Sensors
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Solution Overview
Problem
Conventional row-wise column memory repair in imaging systems is time-consuming and costly due to the need for sequential testing and substitution of defective rows in image sensors.
Innovation Solution
Implementing column-wise memory repair circuitry with multiplexers, latches, and a programmable ROM to bypass defective columns by shifting functional columns, allowing for automatic engagement of spare columns for repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If row-wise column memory repair is performed by sequentially testing and substituting defective rows, then defective columns can be repaired, but the repair process becomes time-consuming and costly
Solution Approach 1:
The patent inverts the conventional row-wise repair approach by implementing column-wise repair. Instead of testing and substituting rows sequentially, the system tests columns and uses spare columns to replace defective ones. This inversion fundamentally changes the repair methodology, enabling parallel processing and significantly reducing repair time while maintaining column memory functionality.
Solution Approach 2:
The patent incorporates spare columns that are pre-configured and ready for immediate substitution of defective columns. During manufacturing, the system performs preliminary testing to identify defective columns and pre-configures the spare columns to replace them. This preliminary action eliminates the need for time-consuming sequential substitution during operation, thereby reducing repair time and costs.
2Reliability
If redundant rows are used for repair substitution, then defective rows can be replaced, but the testing and repair process becomes complex and costly
Solution Approach 1:
The patent simplifies repair circuit complexity by inverting the repair approach from row-wise to column-wise. The column-wise implementation uses a more straightforward multiplexer-based selection mechanism compared to the complex row-wise substitution required in conventional systems. This inversion reduces the overall complexity of the repair circuit while maintaining full repair capability.
Solution Approach 2:
The spare columns in the patent serve multiple functions: they can replace any defective column in the array, and the same spare column infrastructure can handle multiple defect scenarios. This universal approach reduces the need for specialized repair circuits for different defect types, thereby simplifying the overall repair circuit complexity while maintaining comprehensive repair capability.
Data Source
AI summary
An image sensor may include an array of image pixels arranged in rows and columns. Each image pixel arranged along a column may be coupled to a pixel column line. Each pixel column line may be coupled to column memory circuitry via a respective analog-to-digital converter circuit. The column memory circuitry may include multiple column memory circuits, including a spare column memory circuit. If none of the column memory circuits are defective, the spare column memory circuit is idle. If one of the column memory circuits is defective, the spare column memory circuit is engaged to bypass the defective column memory circuit. Configured in this way, the column memory circuitry is provided with column-wise memory repair capabilities.