Non-Volatile Memory Monitoring Cell Dynamic Read Voltage Adjustment
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Solution Overview
Problem
Conventional flash memory devices, particularly multi-level cell (MLC) systems, face issues with data retention due to charge leakage, leading to reduced read margins and increased likelihood of erroneous data interpretations, as the threshold voltage distributions shift and broaden over time.
Innovation Solution
A non-volatile memory device with a monitoring memory cell and a method that adjusts the read voltage based on preliminary read operations, using a first read voltage to determine if data has changed, and setting a main read voltage differently to accurately read data from memory cells, thereby minimizing errors caused by charge leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed read voltage is used in MLC flash memory, then the device structure remains simple and operation is easy, but charge leakage causes threshold voltage shifts that lead to increased data read errors and reduced reliability
Solution Approach 1:
The patent implements dynamic read voltage adjustment by introducing a voltage generation unit that varies the read voltage level based on the retention time of stored data. As charge leakage occurs over time causing threshold voltage shifts, the system automatically adjusts the read voltage to compensate, transforming the static read voltage approach into a dynamic adaptation mechanism that maintains reading accuracy throughout the data retention period
Solution Approach 2:
The system employs feedback mechanisms where the controller monitors data integrity and adjusts read voltage levels accordingly. By detecting threshold voltage shifts caused by charge leakage and responding with appropriate voltage adjustments, the system creates a closed-loop control that maintains reliable data reading despite temporal degradation effects
2Measurement precision
If multiple read voltages are used to compensate for threshold voltage shifts, then data reading accuracy improves, but the operation time and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-establishing multiple read voltage levels and their corresponding usage conditions based on retention time. The voltage generation unit is pre-configured with different voltage levels, and the controller selects the appropriate voltage level in advance based on when the data was written, eliminating the need for iterative voltage searching and reducing the time penalty associated with multiple voltage adjustments
Data Source
AI summary
A non-volatile memory device and related method of driving data are disclosed. The non-volatile memory device includes an array of multi level cells and a monitoring memory cell. The method of driving including performing a preliminary read operation with respect to a monitoring memory cell using a first read voltage, determining whether data initially stored in the monitoring memory cell is identical with data read from the monitoring memory cell during the preliminary read operation, and setting a main read voltage to a level different from the level of the first read voltage when the data initially stored in the monitoring memory cell is not identical with the data read from the monitoring memory cell in relation to the first read voltage.