Memory Array Error Repair Circuitry
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Solution Overview
Problem
Existing memory array repair schemes, such as CRESTA, are expensive in terms of area requirements due to the increasing number of potential solutions with more redundant rows and columns, and require significant logic to implement, making them inefficient for large-scale error correction.
Innovation Solution
A memory array with error detection and repair circuitry that analyzes addressed words to determine if errors are single or multiple, preferentially selecting a redundant row for multiple errors and a redundant column for single errors, optimizing the use of repair resources and reducing the area required for logic implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a covering algorithm is used to arrange redundant rows and columns to cover the maximum number of errors, then the number of errors corrected is maximized, but the area cost becomes expensive
Solution Approach 1:
The patent applies partial action by analyzing only the addressed word containing errors rather than performing a complete covering algorithm analysis of the entire memory array. This selective approach identifies multiple errors in the current word and repairs them using available redundant rows or columns, achieving effective error correction without the computational overhead and area cost of exhaustive algorithms.
2Reliability
If the CRESTA scheme is used to deterministically find the best repair solution by trying spare rows and columns in different orders, then the repair effectiveness is improved, but the area required for logic increases considerably
Solution Approach 1:
The patent extracts and focuses only on the essential information needed for repair decision-making: the pattern of errors within the addressed word. By taking out only the relevant error data from the word and analyzing it locally, the system avoids the complex logic required by CRESTA to systematically try all permutations of spare rows and columns, thereby reducing device complexity while maintaining repair effectiveness.
Solution Approach 2:
The error repair circuitry performs self-service by autonomously analyzing the error pattern in the addressed word and independently deciding whether to use a redundant row or column based on the detected error configuration. This self-contained approach eliminates the need for complex external control logic that would be required to implement the full CRESTA algorithm.
3Reliability
If more redundant rows and columns are added to handle increasing errors, then the error coverage is improved, but the number of potential solutions increases dramatically making the scheme more expensive in area
Solution Approach 1:
The patent applies local quality by making repair decisions based on the local error pattern within the addressed word rather than considering global arrangements of all redundant resources. The error repair circuitry analyzes the specific configuration of errors in the current word and selects appropriate redundant rows or columns based on this local information, enabling effective use of redundant resources without the combinatorial complexity that arises from trying to optimize global solution spaces.
Data Source
AI summary
A memory array comprises a plurality of rows and a plurality of columns, each row comprising at least one addressable word. The memory array comprises at least one redundant row and at least one redundant column. Error detection circuitry analyzes the memory array by addressing words and detecting errors within the addressed words. Error repair circuitry selects for a detected error either a redundant row or a redundant column to replace one of the row or column containing the error. It is determined for the detected error whether the error is a single error bit in the addressed word or whether it is one of a plurality of error bits within the word. If the error is the latter, then the error repair circuitry preferentially selects a redundant row rather than a redundant column to repair the error.