NAND Read Bias Tuning Using ECC Failure Feedback
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Solution Overview
Problem
Data storage devices face challenges in accurately reading data from nonvolatile memory devices due to variations in threshold voltage distributions, leading to errors and inefficiencies in error correction, which existing technologies fail to address effectively.
Innovation Solution
A data storage device with a controller that iteratively adjusts the read bias based on previous read operations and correction failure indexes, using error correction algorithms like BCH and TPC to minimize error rates by setting a final read bias corresponding to a minimum correction failure index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed read bias is used for reading data from nonvolatile memory, then the read operation is simple and fast, but the data read accuracy deteriorates due to threshold voltage variations
Solution Approach 1:
The patent implements dynamic read bias adjustment by iteratively modifying the read bias based on correction failure indexes from error correction operations. The controller adjusts the read bias in multiple iterations, selecting the bias that produces the minimum correction failure index, thereby adapting to threshold voltage variations and improving data read accuracy.
Solution Approach 2:
The system uses feedback from the error correction operation results (correction failure indexes) to adjust the read bias. The controller monitors the correction failure index from each read operation and uses this feedback to modify the read bias in subsequent iterations, creating a closed-loop system that continuously optimizes read accuracy.
2Measurement precision
If error correction operations are performed multiple times to improve data accuracy, then the data read accuracy improves, but the read time increases
Solution Approach 1:
The patent performs error correction operations a limited number of times (e.g., 1-3 iterations) rather than continuously. The controller stops the iterative read operations when a predetermined number of iterations is reached or when the correction failure index becomes sufficiently low, balancing data accuracy improvement with acceptable read time.
3Reliability
If the read bias is adjusted based on previous read operations and correction failure indexes, then the error rate decreases, but the processing complexity increases
Solution Approach 1:
The system performs self-optimization by automatically adjusting the read bias based on its own error correction results. The controller monitors correction failure indexes from its own read operations and autonomously modifies the read bias without external intervention, enabling the system to adapt to memory characteristics and improve reliability independently.
Data Source
AI summary
A data storage device includes a nonvolatile memory device including a target memory region; and a controller suitable for performing a read operation by reading a data chunk from the target memory region based on a read bias and performing an error correction operation for the data chunk, iterating the read operation according to a result of the error correction operation, and adjusting the read bias based on at least one read bias used in one or more previous read operations and at least one correction failure index corresponding to the at least one read bias.