Flash Memory Block Remapping Using Functional Blocks for Defect Identification
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Solution Overview
Problem
Existing flash memory devices face challenges in efficiently identifying and remapping defective blocks without requiring a large number of dedicated fuse circuits, especially as the number of memory blocks increases, leading to space occupancy issues and user involvement in identifying bad blocks.
Innovation Solution
A block remapping system that uses a limited number of fuse sets to identify and remap defective blocks, allowing transparent operation by translating addresses from bad blocks to good blocks, thereby eliminating the need for user adaptation and reducing the number of dedicated fuse circuits needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of dedicated fuse circuits are used to identify defective blocks, then the reliability of defect identification is improved, but the space occupancy and device complexity increase
Solution Approach 1:
The patent applies universality by enabling good memory blocks to serve dual purposes: normal data storage and defect identification. Instead of dedicating separate fuse circuits for identifying each defective block, the system uses the functional blocks themselves to store identification data about defective blocks. This multi-functional approach eliminates the need for separate identification hardware, reducing space occupancy while maintaining reliable defect identification.
Solution Approach 2:
The patent uses copying by storing copies of defective block address information in the good blocks rather than using dedicated fuse circuits. The identification data is copied into the functional memory blocks, which then serve both as data storage and as the identification mechanism. This eliminates the need for separate fuse circuits and reduces overall device complexity.
2Reliability
If traditional fuse-based remapping is used, then defective blocks can be identified and remapped, but the number of fuse circuits increases with the number of memory blocks
Solution Approach 1:
The patent makes functional blocks universal by having them perform both data storage and defect identification functions. Good blocks store identification information about defective blocks, eliminating the need for separate fuse circuits. This reduces device complexity while maintaining the remapping capability, as the identification data is now distributed across functional blocks rather than requiring dedicated fuse circuits for each defective block.
Solution Approach 2:
The patent discards the traditional fuse circuit approach and recovers space by using existing functional blocks for identification purposes. Instead of adding dedicated fuse circuits, the system recovers the use of good blocks to also serve as identification storage, thereby reducing overall device complexity while maintaining remapping functionality.
3Ease of manufacture
If bad blocks are identified during manufacturing, then defective blocks can be remapped, but users must be involved in identifying and adapting to bad blocks
Solution Approach 1:
The patent implements self-service by enabling the memory system to automatically identify and remap defective blocks without user involvement. Good blocks automatically store identification data about defective blocks, and the system autonomously performs remapping operations. This eliminates the need for users to manually identify or adapt to bad blocks, improving ease of operation while maintaining manufacturing-side defect identification capabilities.
Solution Approach 2:
The patent applies preliminary action by pre-storing defective block identification data in good blocks during manufacturing. This preliminary storage of remapping information enables the system to automatically handle defective blocks during normal operation without requiring user adaptation. The identification data is prepared in advance in the functional blocks, allowing seamless automatic remapping.
Data Source
AI summary
A non-volatile memory device includes a block remapping system that offsets an input block address by the addresses of non-functional blocks to provide an output block address that is used to address the memory device. The system generates the output block addresses by, in effect, adding to the input block address the addresses of all non-functional blocks of memory that are between an initial address and the output block address. The system performs this function be comparing the input block address to the address of any defective block. If the address of the defective block is less than or equal to the input block address, the addresses of all defective blocks starting at the block address are added to the input block address. The system then iteratively performs this process using each output block address generated by the system in place of the input block address.