Memory Temperature Logging for Accurate NAND Read Compensation
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Solution Overview
Problem
Extreme temperatures affect the data retention capabilities of memory devices, particularly NAND-based cells like QLCs, leading to inaccurate data reading and unreliable temperature metadata, which can result in failed operations such as copyback operations.
Innovation Solution
Implementing a temperature log separate from the data, where temperature information is stored in lower-level cells less susceptible to temperature effects, allowing for accurate temperature compensation during read operations by tracking temperature ranges and applying appropriate corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If temperature metadata is stored with data in the same memory cells, then data storage capacity is maximized, but temperature information becomes unreliable at extreme temperatures
Solution Approach 1:
The patent segments the storage system into two distinct parts: primary storage for data in higher-level memory cells (e.g., QLCs) and a separate temperature log in lower-level memory cells (e.g., SLCs). This segmentation allows temperature metadata to be stored independently from data, ensuring temperature information reliability while maintaining maximum data storage capacity in the primary storage medium.
Solution Approach 2:
The patent introduces a temperature log as an intermediary storage structure that mediates between the data storage requirements and temperature tracking needs. This intermediary component stores temperature metadata separately, acting as a reliable reference that is not affected by the temperature susceptibility of the primary data storage cells.
2Quantity of substance
If data is written to higher-level memory cells for increased storage density, then storage capacity is improved, but data retention accuracy deteriorates at extreme temperatures
Solution Approach 1:
The patent divides the storage hierarchy into higher-level cells (QLCs, MLCs) for high-density data storage and lower-level cells (SLCs) for accurate temperature logging. This segmentation allows each layer to perform its optimized function: maximum storage density in higher-level cells and reliable temperature tracking in lower-level cells, resolving the contradiction between density and temperature stability.
Solution Approach 2:
The patent changes the operational parameters of different memory cell types by using higher-level cells for data storage (accepting their temperature sensitivity) and lower-level cells for temperature metadata (utilizing their temperature stability). This parameter differentiation allows the system to leverage the strengths of each cell type while mitigating their weaknesses.
3Reliability
If a separate temperature log is implemented, then temperature tracking reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by using the lower-level memory cells to serve dual purposes: as part of the overall storage capacity and as a dedicated temperature log. This universal usage of existing memory cells for both data and temperature metadata reduces device complexity while maintaining temperature tracking reliability.
Solution Approach 2:
The system performs self-service by automatically tracking and logging temperature metadata during normal write operations without requiring separate dedicated hardware or complex external monitoring systems. The memory system itself generates and maintains the temperature log, reducing overall device complexity while ensuring reliable temperature tracking.
Data Source
AI summary
A memory system may store temperature exception tracking in a temperature log, which may be separate from data to which the temperature information corresponds. A memory device may store data in a relatively higher-level cell and the corresponding temperature information in a relatively lower-level cell. To perform a write operation, the memory system may determine a current temperature at which the data is being written or was written to a partition of a memory device and may indicate in the temperature log if the current temperature is entering a temperature range that is outside a threshold temperature (e.g., a nominal temperature). To perform a read operation, the memory system may determine if the data to read was written to the memory device outside the threshold temperature to determine whether to perform temperature compensation for the read operation.