Memory Column Redundancy via Static Multiplexer Shifting
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Solution Overview
Problem
Existing column redundancy schemes in memories, such as sense amplifier shifting, require complex control logic and dynamic switching, which leads to inefficiencies in die savings and power consumption, while I/O shifting is less dense and more complex to implement.
Innovation Solution
A column redundancy scheme using a single redundant column and static 2:1 multiplexers that do not shift based on word type, allowing for simplified control logic and reduced switching losses by arranging columns in order with the redundant column at the end, enabling selection between corresponding and subsequent columns without dynamic shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sense amplifier shifting is used for column redundancy, then memory density is improved, but control logic complexity increases
Solution Approach 1:
The patent applies dynamics by making the multiplexer configuration dynamic rather than static. The 2:1 multiplexers are configured based on the defective column position detected during testing, allowing the system to adapt its read path dynamically. This resolves the contradiction by maintaining high density through flexible column substitution while simplifying control logic through automated defect detection and configuration.
Solution Approach 2:
The patent changes the configuration parameter of the multiplexers based on the defective column position. During testing, the system identifies which column is defective and configures the multiplexers accordingly to route reads from subsequent columns. This parameter change approach allows the same hardware structure to serve multiple redundancy purposes without requiring complex control logic for each scenario.
2Reliability
If dynamic switching is used in multiplexers for sense amplifier shifting, then column redundancy is achieved, but switching power losses increase
Solution Approach 1:
The patent performs preliminary configuration of the multiplexers during the testing phase. The defective column position is identified early, and the multiplexer configuration is established before normal read operations begin. This preliminary action eliminates the need for dynamic switching during operational reads, thereby reducing switching power losses while maintaining column redundancy capability.
Solution Approach 2:
The patent implements periodic testing to identify defective columns, followed by a stable configuration phase for normal operations. The testing occurs periodically (e.g., during initialization or at scheduled intervals), and once a defective column is identified, the multiplexer configuration remains stable for subsequent reads. This periodic testing followed by stable operation reduces continuous switching activity and associated power losses.
3Device complexity
If I/O shifting is used for column redundancy, then control logic is simplified, but memory density decreases
Solution Approach 1:
The patent segments the memory columns into groups associated with different multiplexers, where each multiplexer handles a specific range of column substitutions. This segmentation allows the use of a single redundant column to replace multiple defective columns across different positions, achieving high density while maintaining relatively simple control logic for each segmented group.
Solution Approach 2:
The patent makes the redundant column universal by allowing it to serve multiple purposes through multiplexer configuration. A single redundant column can replace any defective column in its associated group, depending on which column is found to be defective during testing. This multi-functionality approach achieves high memory density without requiring separate redundant columns for each position, thereby avoiding excessive control logic complexity.
Data Source
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Figure 3A
AI summary
A memory includes a plurality of columns and a redundant column. The memory includes a plurality of multiplexers corresponding to the plurality of columns. Depending upon the location of a defect, the multiplexers are configured to select for their corresponding column or an immediately-subsequent column to their corresponding column.