NAND Flash Memory Temperature Error Management
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Solution Overview
Problem
NAND flash memory devices experience increased bit error rates and reliability issues due to temperature variations between the time of data writing and reading, leading to unnecessary memory cell retirement and data refresh, which can reduce drive performance and capacity.
Innovation Solution
Incorporating a write temperature indicator appended to stored data and using a controller to determine the numerical temperature difference between write and read temperatures, allowing for targeted error management operations such as memory cell retirement and data refresh, thereby reducing the occurrence of undesirable outcomes like increased write amplification and drive size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature-related error management is implemented without write temperature indicators, then error detection capability is improved, but false positives increase leading to unnecessary memory cell retirement
Solution Approach 1:
The patent applies preliminary action by storing the write temperature indicator at the time of programming data to the memory cell. This pre-recorded temperature information is then used during read operations to compare with the current read temperature, enabling the system to distinguish between temperature-induced errors and actual memory defects. This preliminary recording of temperature conditions prevents false positive errors during error management operations.
2Reliability
If memory cells are retired based on error rates without temperature consideration, then data integrity is improved, but drive capacity is reduced
Solution Approach 1:
The patent applies parameter changes by introducing temperature as an additional parameter in the error management decision process. Instead of relying solely on error rates, the system now considers both the error rate and the temperature difference between write and read operations. This multi-parameter approach allows the system to maintain data integrity while avoiding unnecessary retirement of memory cells that exhibit errors only under temperature variations, thereby preserving drive capacity.
3Reliability
If data refresh operations are performed frequently to maintain reliability, then data retention is improved, but write amplification increases
Solution Approach 1:
The patent applies feedback by using the temperature difference information to dynamically adjust the error management strategy. When the temperature difference between write and read operations is small, the system can be more conservative with refresh operations. When the temperature difference is large, the system can perform refresh operations more aggressively or adjust read reference voltages. This feedback-based approach ensures data retention while minimizing unnecessary write amplification from excessive refresh operations.
Data Source
AI summary
Apparatuses and methods for temperature related error management are described. One or more apparatuses for temperature related error management can include an array of memory cells and a write temperature indicator appended to at least one predetermined number of bytes of the stored data in the array of memory cells. The apparatuses can include a controller configured to determine a numerical temperature difference between the write temperature indicator and a read temperature indicator and determine, from stored operations, an error management operation for the stored data based, at least in part, on comparison of the numerical temperature difference to a temperature difference threshold.