NAND Memory Read Voltage Prediction for Valley Accuracy
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Solution Overview
Problem
The accuracy of reading data stored in NAND memory cells is affected by the variation of stored charges over time and repeated read operations, as well as temperature fluctuations, leading to inaccuracies in data retrieval.
Innovation Solution
A memory device and system that utilize a peripheral circuit to determine a target valley voltage through a function model, such as a quadratic function, based on multiple read voltages and results to improve data reading accuracy by predicting the optimal read voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional read operations are used with fixed read voltages, then the device complexity is low and operation is simple, but the data reading accuracy deteriorates due to charge variation over time and temperature
Solution Approach 1:
The system performs preliminary actions by obtaining multiple first results at different target read voltages before determining the final target valley voltage. This preliminary data collection at various voltages enables accurate prediction of the optimal read voltage, improving data reading accuracy while the automated process manages the increased operational steps
Solution Approach 2:
The system implements feedback by using the obtained first results from multiple read voltages to predict and determine the optimal target valley voltage. This feedback mechanism continuously adjusts the read voltage based on actual read results, ensuring high reading accuracy while the automated feedback loop manages the complexity of multiple voltage measurements
2Measurement precision
If multiple read voltages are used to improve reading accuracy, then the data retrieval precision improves, but the operation time and processing steps increase
Solution Approach 1:
Multiple first results are obtained at different target read voltages as preliminary data collection before determining the final target valley voltage. This preliminary measurement at various voltages enables accurate prediction, improving reading precision while the systematic approach efficiently manages the time required for multiple measurements
Solution Approach 2:
The system changes the read voltage parameter to multiple different target read voltages when obtaining first results. By systematically varying this parameter and using it to predict the optimal target valley voltage, the system achieves high reading accuracy while the automated parameter adjustment manages the increased measurement time
Data Source
AI summary
According to one aspect of the present disclosure, a memory device is provided. The memory device may include a memory cell array including a plurality of memory cells. A preset number of the memory cells may form a code word. The memory device may include a peripheral circuit coupled with the memory cell array. The peripheral circuit may be configured to obtain M first results corresponding to at least one code word at M target read voltages. The peripheral circuit may be configured to obtain a predicted valley voltage according to the M first results and the M target read voltages in conjunction with a preset function model. The peripheral circuit may be configured to determine a target valley voltage based on the predicted valley voltage. The target valley voltage may be configured as a read voltage for a read operation on the at least one code word.