Flash Memory Read Voltage Adjustment for Threshold Shift
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Solution Overview
Problem
Flash memory devices experience deteriorated read performance due to changes in threshold voltages of memory cells over time, leading to unreliable read operations and increased error correction decoding failures.
Innovation Solution
A method is introduced to dynamically adjust the read parameter, specifically the read voltage, based on current cell conditions by counting the number of ones or zeroes in the data, allowing for real-time updates and optimization of read operations without requiring additional retry operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed read parameter is used for reading data from flash memory, then the initial read operation can be performed, but the read performance deteriorates over time due to threshold voltage changes in memory cells
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed read parameter to a dynamically adjustable read parameter. The read parameter is updated based on the distribution characteristics of read data, allowing the system to adapt to threshold voltage changes in memory cells over time, thereby maintaining reliable read operations without requiring additional retry operations.
Solution Approach 2:
The patent implements feedback by using the distribution characteristics of read data (such as the count of ones or zeroes) to determine and update the read parameter. This feedback mechanism enables the system to continuously optimize the read parameter based on actual memory cell conditions, improving read performance while reducing time loss from retries.
2Productivity
If the read parameter is updated based on data distribution characteristics, then read performance is improved, but the system complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the read parameter (such as read voltage or threshold values) based on the distribution characteristics of read data. This approach improves read operation efficiency by adapting parameters to current memory cell states while maintaining a relatively simple implementation through straightforward statistical analysis of read data.
3Reliability
If traditional error correction decoding is performed without parameter optimization, then the process is simple, but decoding failures increase due to threshold voltage changes
Solution Approach 1:
The patent applies preliminary action by updating the read parameter before performing error correction decoding. By optimizing the read parameter based on data distribution characteristics in advance, the system improves the success rate of error correction decoding while avoiding the need for complex retry mechanisms, thus enhancing reliability without significantly increasing decoding process complexity.
Data Source
AI summary
A memory system including a non-volatile memory device and a memory controller is provided. When a read operation on a first data initially output from the non-volatile memory device during a first read operation is successful, the memory controller may change a read voltage for reading a second data stored in the non-volatile memory device during a second read operation.