Memory Controller Adaptive Read Voltage Adjustment
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Solution Overview
Problem
Memory systems face challenges in accurately reading data due to changes in threshold voltage of memory cell transistors, leading to erroneous data determination and the need for repeated read operations with varying read voltages to correct errors.
Innovation Solution
A memory system with a controller that executes multiple read operations using different read voltages, error correction, and shift pattern measurement operations to update shift patterns in a shift index table, allowing for adaptive read voltage adjustments to minimize error bits and ensure accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the read voltage value is changed to correct erroneous data determination, then data accuracy is improved, but the number of read operations increases
Solution Approach 1:
The system performs a measurement operation before the actual read operation to determine the appropriate read voltage value. This preliminary action identifies the optimal read voltage based on threshold voltage distribution, preventing erroneous data determination in subsequent read operations and reducing the need for retries.
Solution Approach 2:
The system uses error correction results as feedback to adjust the read voltage value. When error correction indicates erroneous data determination, the system modifies the read voltage and retries the read operation, creating a feedback loop that continuously optimizes data accuracy while minimizing unnecessary operations.
2Reliability
If multiple read operations with different read voltages are executed, then data accuracy is improved, but operation complexity increases
Solution Approach 1:
The measurement operation is executed beforehand to establish the appropriate read voltage value, simplifying subsequent read operations. By determining the optimal read voltage in advance based on threshold voltage distribution characteristics, the system avoids complex real-time adjustments during actual data reading.
3Reliability
If the read voltage value is dynamically adjusted, then error bits are reduced, but measurement and control complexity increases
Solution Approach 1:
The system performs self-measurement of threshold voltage distribution through the measurement operation and automatically determines the appropriate read voltage value without external intervention. This self-service capability enables dynamic adaptation to changing memory characteristics while maintaining operational simplicity through automated decision-making.
Data Source
AI summary
According to one embodiment, a memory system includes a non-volatile first memory with first storage areas. A controller executes a first read operation on a second storage area of the first storage areas. When an error correction in the first read operation fails, the controller acquires a first measured value being a value of a read voltage for suppressing the number of occurrences of error bits in the second storage area. The controller updates, on the basis of the first measured value, one of first candidate values of the read voltage with a second candidate value. When the error correction in a second read operation for a third storage area of the first storage areas fails, the controller executes the read operation once or more on the third storage area by using, as the read voltages, different first candidate values of the first candidate values.