Flash Memory Read-Level Estimation from Threshold Valley Crossings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As data storage capacity and bit density increase in flash memories, the margins between threshold voltage distributions narrow, leading to errors in calculating the optimal read level, which can cause data reliability issues during re-reading.
Innovation Solution
A memory device with a control logic that calculates an appropriate read level by modeling linear functions based on counting operations and compensating values to improve accuracy, using a combination of high-order and linear functions to determine the optimal read level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data storage capacity and bit density are increased, then storage capacity is improved, but margins between threshold voltage distributions narrow causing calculation accuracy deterioration
Solution Approach 1:
The patent segments the threshold voltage distribution analysis by dividing the read level search into multiple discrete levels (first read level, second read level, third read level, fourth read level). By segmenting the continuous read level parameter into discrete steps, the system can systematically evaluate each level's counting values and identify the optimal read level through comparative analysis, thereby maintaining calculation accuracy even as storage capacity increases and voltage distributions narrow.
Solution Approach 2:
The patent introduces a new dimension of analysis by examining the changes in counting values across multiple read levels rather than relying on a single read level. By analyzing the dimensional relationship between read levels and their corresponding counting values, the system can identify the optimal read level through the valley search method, which provides additional information dimensions to compensate for the narrowed margins in threshold voltage distributions.
2Measurement precision
If multiple read levels are used to improve calculation accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control logic performs self-service by automatically identifying the optimal read level through the valley search method without requiring external intervention or complex manual configuration. The system uses its own counting values from multiple read levels to autonomously determine the optimal read level, which simplifies the overall system complexity while maintaining high measurement precision.
Solution Approach 2:
The patent changes the parameter approach by using the differences and ratios of counting values across multiple read levels as new parameters for optimization. Instead of directly manipulating the threshold voltage distributions, the system transforms the problem into parameter space by analyzing counting value changes, which simplifies the control logic while improving measurement precision through the valley search method.
Data Source
AI summary
Provided is a memory device including a memory cell array including a plurality of cell areas, and a control logic configured to control a calculation operation for an appropriate read level, based on searching for a valley of threshold voltage distributions, in response to an error occurring in a read operation on the cell areas. The control logic, based on a counting operation on data read by using the plurality of read levels, is configured to calculate first through Nth counting values respectively corresponding to first through Nth read levels, calculate a crossing point of at least two linear functions modeled by substituting the first through Nth read levels as inputs and the first through Nth counting values as outputs, and calculate the appropriate read level based on at least one of the read level and a valley height corresponding to a coordinate value of the crossing point.