Flash Memory Page Inversion for Cell-Level Wear Equalization
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Solution Overview
Problem
Conventional flash memory devices experience uneven wear-leveling across memory cells due to the high wear associated with write and erase operations, leading to reduced lifespan, as existing methods primarily focus on block-level wear equalization without considering individual cell differences.
Innovation Solution
A flash memory device and method that employs an inversion determining unit to generate programming pages based on the number of '1's and '0's in data pages or sub-pages, minimizing the number of memory cells changed during operations and reducing wear-leveling stress, using a memory cell array, programming unit, and data verifying unit to restore data pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional block-level wear equalization is used, then erase operation management is simplified, but individual memory cell wear differences are not addressed leading to uneven wear-leveling
Solution Approach 1:
The patent segments the wear equalization process from block-level to memory cell-level by maintaining separate wear counters for each memory cell within a block. This allows individual tracking and management of wear for each cell, enabling more precise wear equalization while still operating at the block level for erase operations.
Solution Approach 2:
The patent applies local quality by treating each memory cell individually with its own wear counter, rather than assuming uniform wear across all cells in a block. This enables differentiated wear management strategies for cells with different wear levels, addressing the uneven wear distribution more effectively.
2Reliability
If more write and erase operations are performed to update data, then data freshness is improved, but memory cell wear increases reducing lifespan
Solution Approach 1:
The patent performs preliminary wear equalization by proactively managing write and erase operations based on individual cell wear counters before wear becomes critical. This allows the system to distribute wear more evenly across all cells, extending overall memory lifespan while maintaining data freshness through controlled updates.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring wear counters for each memory cell and using this information to make intelligent decisions about which cells to update or skip during write operations. This feedback loop allows the system to balance data freshness requirements with wear management, extending memory lifespan.
3Device complexity
If data is stored in original format, then storage simplicity is maintained, but wear concentration on specific cells increases
Solution Approach 1:
The patent applies inversion by reversing the data bits (0 becomes 1, 1 becomes 0) before writing to memory cells. This inversion strategy, combined with wear-aware selection of target cells, helps distribute wear more uniformly across the memory block while maintaining data integrity through the invertible transformation.
4Reliability
If all cells in a block are updated during write operations, then data consistency is ensured, but unnecessary wear on already-updated cells increases
Solution Approach 1:
The patent applies partial action by updating only the necessary portion of memory cells during write operations rather than forcing updates to all cells in a block. By using wear counters to identify which cells actually need updating, the system reduces unnecessary wear stress while maintaining data consistency for the updated portion.
Data Source
AI summary
Disclosed are a flash memory device and flash memory programming method that equalizes a wear-level. The flash memory device includes a memory cell array, an inversion determining unit to generate a programming page through inverting or not inverting a data page based on a number of ‘1’s and ‘0’s in the data page, a programming unit to store the generated programming page in the memory cell array; and a data verifying unit to read the programming page stored in the memory cell array, to restore the data page from the programming page according to whether an error exists in the read programming page, and to output the restored data page, and thereby can equalize a wear-level of a memory cell.