Backup Circuit for Multi-Level Flash Memory Data Integrity
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Solution Overview
Problem
Conventional flash memory systems incorporating multi-level cells are prone to the loss of Least Significant Bit (LSB) data during the programming of Most Significant Bit (MSB) data, as the previously programmed LSB data is not retained in the buffer memory and cannot be easily repaired.
Innovation Solution
A memory system with a backup memory that temporarily stores LSB data before programming MSB data, allowing for re-programming of LSB data if a failure occurs during the MSB programming process, and utilizing error correction codes to repair damaged LSB data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level cells are used to increase storage capacity, then data storage capacity is improved, but reliability deteriorates due to LSB data loss during MSB programming
Solution Approach 1:
The patent applies preliminary action by storing the LSB data in the buffer memory before performing the MSB programming operation. This preliminary preservation of LSB data ensures that if programming failure occurs during MSB writing, the LSB data is already saved and can be re-programmed without loss, thus maintaining data integrity while enabling multi-level cell storage.
2Device complexity
If LSB data is not stored in buffer memory to reduce complexity, then device complexity is reduced, but reliability deteriorates due to inability to repair damaged LSB data
Solution Approach 1:
The patent implements preliminary action by pre-storing LSB data in the buffer memory before MSB programming. This simple preliminary step enables subsequent repair capability without requiring complex backup mechanisms, achieving reliability improvement with minimal additional complexity.
Solution Approach 2:
The patent uses copying by creating a copy of the LSB data in the buffer memory before the critical MSB programming operation. This copy serves as a backup that can be used to repair damaged LSB data, providing reliability without requiring complex redundant storage structures.
3Productivity
If conventional programming operation is used without backup, then programming time is reduced, but reliability deteriorates due to data loss on programming failure
Solution Approach 1:
The patent applies preliminary action by saving LSB data in the buffer memory before MSB programming. This preliminary preservation enables fast programming operations while ensuring data retention capability, as the backup is prepared in advance without adding significant time overhead to the programming process.
Data Source
AI summary
Provided are a memory system and a program method. The memory system includes a flash memory and a memory controller. The flash memory stores first bit data and then stores second bit data in a multi-level memory cell. The memory controller includes a buffer memory temporarily storing the first bit data and the second bit data, and a backup memory storing the first bit data while the flash memory is storing the second bit data. The backup memory re-programs the first bit data to the flash memory upon detecting a program failure associated with the storing the second bit data.