Nonvolatile Memory Controller LSB Backup Strategy
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Solution Overview
Problem
Nonvolatile memory devices face challenges in maintaining data integrity during multi-level cell programming, particularly due to sudden power-offs, which can damage lower-bit data stored in memory cells as a result of upper-bit data writing, leading to errors and increased recovery times.
Innovation Solution
A nonvolatile memory device with a controller that manages data by storing information about invalidated or backed-up data in spare areas, allowing for skipping of recovery operations on invalidated pages and rapid location of backup data during power failures, using a mapping table to manage logical and physical addresses and determine whether pages are LSB or MSB pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If MLC programming is performed to increase storage capacity, then storage capacity is improved, but data integrity deteriorates due to LSB damage from MSB writing
Solution Approach 1:
The patent performs preliminary backup of LSB data to a spare area before MSB programming begins. This advance preparation ensures that if power failure occurs during MSB writing, the original LSB data can be recovered, thus preventing data integrity loss while maintaining MLC storage capacity enhancement
Solution Approach 2:
The patent creates a protective backup copy of LSB data in the spare area before the harmful MSB programming operation. This cushioning mechanism acts as a safety net that protects against potential LSB damage from sudden power-off during MSB writing, thereby maintaining data integrity while enabling increased storage capacity through MLC operation
2Reliability
If backup operation is performed on all LSB pages before MSB programming, then data integrity is improved, but programming time increases
Solution Approach 1:
The patent applies backup operation selectively only to LSB pages that will share word lines with upcoming MSB programming operations, rather than universally backing up all LSB pages. This localized approach maintains data integrity for affected pages while significantly reducing unnecessary backup time and overhead
Solution Approach 2:
The patent changes the backup scope parameter from 'all LSB pages' to 'only relevant LSB pages sharing word lines with MSB pages'. This parameter optimization maintains sufficient data protection while reducing the time loss associated with excessive backup operations
3Reliability
If recovery operation is performed on all LSB pages after power restoration, then data integrity is improved, but recovery time increases
Solution Approach 1:
The patent performs recovery operation selectively only on LSB pages that shared word lines with MSB programming operations, rather than recovering all LSB pages. This localized recovery approach maintains data integrity for affected pages while minimizing unnecessary recovery time
Solution Approach 2:
The patent skips recovery operations on LSB pages that were not affected by MSB programming (i.e., pages that did not share word lines). By identifying and skipping these unaffected pages, the system rapidly completes recovery for only the necessary pages, thereby maintaining data integrity while significantly reducing total recovery time
Data Source
AI summary
Disclosed is a nonvolatile memory device which includes a nonvolatile memory including a plurality of LSB and MSB pages at a plurality of wordlines; and a controller controlling the nonvolatile memory. The controller controls the nonvolatile memory such that an LSB program operation on a first wordline of the plurality of wordlines is programmed and then an LSB program operation on a second wordline of the plurality of wordlines is programmed. When the LSB program operation on the second wordline is performed, the nonvolatile memory stores information about LSB data programmed at the first wordline at a spare area of the second wordline.