Nonvolatile Memory Read Voltage Adjustment via History Table
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Solution Overview
Problem
Flash memory devices often experience errors due to various factors, leading to unreliable data storage and retrieval, particularly when uncorrectable errors occur, which existing technologies have not adequately addressed in terms of improving read operation reliability and performance.
Innovation Solution
A nonvolatile memory system and memory controller method that adjusts read voltages using a read history table, detecting optimal read voltage sets based on reliability parameters such as error bits, temperature, and read count, and updates the table to improve data retrieval accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fixed read voltages are used, then the read operation is simple and fast, but errors occur due to various factors leading to unreliable data retrieval
Solution Approach 1:
The system performs preliminary actions by maintaining a read history table that stores optimal read voltage information from previous read operations. Before executing a read operation, the system queries this table to obtain pre-determined voltage adjustments based on historical data about the memory device's behavior under similar conditions, thereby proactively compensating for potential errors rather than reacting to them after they occur.
Solution Approach 2:
The system implements feedback by continuously updating the read history table with results from actual read operations. When read errors occur or when optimal voltages are identified through retry mechanisms, this information is fed back into the table, which then guides future voltage selection. This closed-loop feedback system enables the device to learn from past operations and progressively improve read reliability.
2Reliability
If read voltages are adjusted based on read history, then read operation reliability improves, but the read operation time increases due to additional processing
Solution Approach 1:
Optimal read voltage information is prepared in advance and stored in the read history table during previous operations or during idle periods. When a read operation is initiated, the system simply queries this pre-computed information rather than performing complex voltage optimization calculations in real-time, thereby achieving reliable reads without significant time penalty.
Solution Approach 2:
The system serves itself by automatically maintaining and updating the read history table without requiring external intervention or complex external control mechanisms. The memory device uses its own read operation results to populate and refine its voltage adjustment strategies, enabling autonomous optimization that minimizes overhead time.
3Reliability
If repeated read operations are performed to ensure data accuracy, then data retrieval reliability improves, but productivity decreases due to multiple read attempts
Solution Approach 1:
The system performs preliminary voltage optimization by consulting the read history table before each read operation to determine the most appropriate voltage settings in advance. This pre-adjustment significantly reduces the probability of read errors, thereby minimizing the need for repeated read attempts and improving overall data retrieval efficiency while maintaining high accuracy.
Solution Approach 2:
The read history table accumulates feedback from successful and unsuccessful read operations, allowing the system to learn which voltage settings work best under specific conditions. This feedback mechanism enables the system to progressively reduce the frequency of read errors and subsequent retry operations, thereby improving productivity over time while maintaining data accuracy.
Data Source
AI summary
An operating method of a nonvolatile memory system includes receiving a read request for at least one page from a host. Upon receiving the read request, read voltages are adjusted using a read history table to perform a first read operation in which data stored at the nonvolatile memory is read. An optimal read voltage set is detected when data read according to the first read operation includes an uncorrectable error, and a second read operation is performed in which the stored data is read based on the detected optimal read voltage set. The read history table is updated based on a reliability parameter indicating a characteristic of the nonvolatile memory, a characteristic of the data at the first or second read operation, the optimal read voltage, or the read history table.