Adaptive Self-Refresh Thresholds for NAND Memory Areas
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Solution Overview
Problem
NAND storage devices face issues with bit errors due to long periods of inactivity or repeated data access, leading to either excessive self-refreshing and wear or inadequate refreshing, resulting in data loss.
Innovation Solution
A NAND storage device with a built-in controller that sets distinct self-refresh thresholds for different memory areas based on their characteristics, allowing for adaptive refreshing to minimize bit errors and data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low threshold value for self-refreshing is used, then bit errors are corrected more frequently, but the self-refreshing is performed more than required leading to worse degradation or wear of cells
Solution Approach 1:
The patent applies local quality by differentiating memory areas into multiple regions with different refresh thresholds based on their specific characteristics and data retention requirements. Each memory area receives customized refresh policies rather than a uniform approach, allowing critical data to be refreshed more frequently while less critical data uses lower refresh rates, thereby balancing reliability and cell wear concerns.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting refresh thresholds based on measured bit error rates and data characteristics. The system monitors actual error conditions and modifies refresh parameters accordingly, transitioning from static fixed thresholds to adaptive dynamic thresholds that respond to real-time memory state, optimizing the balance between error correction and wear prevention.
2Duration of action of stationary object
If a high threshold for self-refreshing is used, then cell wear is reduced, but power is turned off without refreshing for extended periods leading to increased bit errors and data loss
Solution Approach 1:
The patent applies local quality by differentiating memory areas into multiple regions with different refresh thresholds based on their specific characteristics and data retention requirements. Each memory area receives customized refresh policies rather than a uniform approach, allowing critical data to be refreshed more frequently while less critical data uses lower refresh rates, thereby balancing reliability and cell wear concerns.
Solution Approach 2:
The patent implements dynamics by making refresh thresholds adjustable and adaptive rather than fixed. The system dynamically modifies refresh parameters based on monitored bit error rates, power state, and data characteristics, enabling the refresh strategy to respond to changing conditions and optimize between cell wear prevention and data retention requirements.
3Device complexity
If uniform self-refreshing is applied to all memory areas, then implementation is simple, but it cannot adapt to different data characteristics leading to excessive or insufficient refreshing
Solution Approach 1:
The patent applies segmentation by dividing the memory space into multiple distinct areas with different refresh characteristics. Each segment is managed independently with its own refresh threshold and policy, allowing the system to tailor refresh behavior to specific data types and retention requirements while maintaining manageable complexity through modular area-based control.
Solution Approach 2:
The patent applies local quality by differentiating memory areas into multiple regions with different refresh thresholds based on their specific characteristics and data retention requirements. Each memory area receives customized refresh policies rather than a uniform approach, allowing critical data to be refreshed more frequently while less critical data uses lower refresh rates, thereby balancing reliability and cell wear concerns.
Data Source
AI summary
A NAND storage device is provided which includes a built-in controller working to compare a bit error in each block of a first memory area of a NAND memory with a first refresh threshold to determine whether data in the first memory area should be self-refreshed. Similarly, the built-in controller also compares a bit error in each block of a second memory area of the NAND memory with a second refresh threshold to determine whether data in the second memory area should be self-refreshed. This structure is capable of setting the refresh thresholds depending on characteristics of data retained in the NAND memory of the NAND storage device.