NAND Memory Read-Voltage Adjustment for Charge-Drift Accuracy
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Solution Overview
Problem
NAND memory devices experience accuracy issues in data reading due to charge fluctuations over time and temperature variations, affecting the reliability of data storage.
Innovation Solution
A memory device with a peripheral circuit that adjusts read voltages within defined boundary voltages to determine a target valley voltage for accurate data reading, using adjustments in both increasing and decreasing directions with varying step sizes to optimize read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read voltage is fixed at a target value, then read operation is simple and fast, but data reading accuracy deteriorates due to charge fluctuations over time and temperature variations
Solution Approach 1:
The patent applies preliminary action by determining boundary voltages and adjusting the target read voltage before actual data reading operations. The peripheral circuit performs voltage adjustments based on stored boundary voltage values to compensate for charge fluctuations and temperature variations, ensuring accurate reading without requiring complex real-time adjustments during each read operation.
Solution Approach 2:
The patent implements feedback mechanisms where the peripheral circuit uses stored boundary voltage information to adjust the target read voltage dynamically. The system incorporates feedback from boundary voltage comparisons and uses this information to optimize reading accuracy, particularly in multi-stage reading operations where boundary voltages guide the adjustment process.
2Adaptability or versatility
If boundary voltage range is expanded, then voltage adjustment flexibility increases, but voltage control precision decreases
Solution Approach 1:
The patent applies segmentation by dividing the voltage adjustment process into multiple stages with different boundary voltage ranges. Each stage has its own optimized boundary voltages stored in the peripheral circuit, allowing the system to handle different reading scenarios with appropriate precision. The segmentation enables coarse adjustment in broader ranges followed by fine adjustment in narrower ranges.
Solution Approach 2:
The patent implements local quality by using different boundary voltage characteristics for different reading stages and conditions. The peripheral circuit stores and applies different boundary voltage values depending on the specific reading operation requirements, optimizing both flexibility and precision for each local context rather than using a single uniform voltage range.
3Reliability
If multiple voltage adjustments are performed, then reading accuracy improves, but read operation time increases
Solution Approach 1:
The patent reduces time loss by performing preliminary determination of boundary voltages and storing them in the peripheral circuit before actual reading operations. This preliminary action eliminates the need for time-consuming voltage adjustments during each read operation, as the boundary voltage information is already available for immediate use.
Solution Approach 2:
The patent applies partial action by performing voltage adjustments selectively based on the specific reading requirements. The system determines whether full multi-stage adjustments are necessary or if simplified adjustments suffice, optimizing the balance between accuracy improvement and time consumption for each reading operation.
Data Source
AI summary
Examples of the present application provide a memory device, memory system, memory controller and operating method thereof, wherein the memory device includes: an array of memory cells, including multiple memory cells, and a preset number of memory cells forming one code word; peripheral circuit coupled to the array of memory cells and configured to: generate a first boundary voltage and a second boundary voltage in accordance with the first result corresponding to at least one code word at a target read voltage; make at least one adjustment to the target read voltage, and obtain the corresponding first result at the adjusted target read voltage after each adjustment; in a process of the adjustment, change a current direction of adjustment to the voltage in accordance with the target read voltage after one adjustment exceeding a range defined by the first boundary voltage and the second boundary voltage.