Memory Controller Block Management for Flash Lifespan
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Solution Overview
Problem
Nonvolatile memory devices, such as NAND flash memory, face reliability and lifespan issues due to charge leakage from floating gates and tunnel oxide breakdown during program/erase cycles, affecting data retention and endurance.
Innovation Solution
A memory managing method that switches between two different management strategies based on the program-erase number of memory blocks, managing by block unit when the number is below a reference value and by word line unit when it exceeds the reference value, using a memory controller with a buffer memory to handle address discontinuity during write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform memory management is applied to all memory blocks, then management simplicity is maintained, but memory lifespan and reliability deteriorate due to inability to address program-erase cycle differences
Solution Approach 1:
The patent segments memory blocks into different management categories based on their program-erase cycle counts. Memory blocks are divided into a first group (below reference value) and a second group (at or above reference value), each managed by different methods. This segmentation allows tailored management strategies that extend lifespan while maintaining manageable complexity through automated classification.
Solution Approach 2:
The patent implements dynamic memory management where the management method changes based on the program-erase number of each block. The system transitions from uniform static management to adaptive dynamic management, switching between block-unit management (for younger blocks) and word-line unit management (for older blocks), thereby optimizing reliability throughout the memory's lifecycle.
2Ease of operation
If block unit management is used for all memory blocks, then management simplicity is maintained, but data integrity deteriorates for blocks exceeding reference program-erase cycles
Solution Approach 1:
The patent segments memory blocks into two groups based on program-erase cycle thresholds. The first group (below reference value) continues to use simple block-unit management for ease of operation. The second group (at or above reference value) switches to word-line unit management to preserve data integrity, as this finer-grained approach allows selective fading out of vulnerable word lines while preserving intact data in healthier portions of the block.
3Reliability
If word line unit management is applied to all memory blocks, then data integrity is improved, but device complexity increases due to address discontinuity handling
Solution Approach 1:
The patent applies word line unit management dynamically only to memory blocks that have reached the reference program-erase cycle threshold, rather than universally. This conditional application maintains data integrity for aging blocks while avoiding the unnecessary complexity of continuous address discontinuity handling for younger blocks that can be managed more simply at the block level.
Solution Approach 2:
The memory controller continuously monitors program-erase cycle counts and uses this feedback to determine which blocks require word line unit management. This feedback mechanism enables the system to automatically adjust management granularity based on actual block aging, maintaining data integrity while minimizing address management complexity through intelligent, data-driven decisions.
Data Source
AI summary
A memory managing method is provided for a memory system, including a nonvolatile memory device and a memory controller controlling the nonvolatile memory device. The memory managing method includes determining whether a program-erase number of a memory block in the nonvolatile memory device reaches a first reference value; managing a life of the memory block according to a first memory managing method when the program-erase number of the memory block is determined to be less than the first reference value; and managing the life of the memory block according to a second memory managing method different from the first memory managing method when the program-erase number of the memory block is determined to be greater than the first reference value.