Simultaneous Multi-Voltage Sense for Analog Memory Read Threshold Estimation
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Solution Overview
Problem
Existing memory devices face challenges in accurately reading analog memory cells due to variations in read thresholds, leading to errors and inefficiencies in data retrieval.
Innovation Solution
A method and system that divide a group of analog memory cells into subsets and apply different sets of read thresholds simultaneously, allowing for the estimation of an optimal set of read thresholds based on quality assessments of the resulting readout results, which can include Error Correction Code metrics and statistical distributions, to improve data reading accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single read threshold is used for all memory cells, then the reading operation is simple and fast, but read errors increase due to variations in cell characteristics
Solution Approach 1:
The patent divides the memory cell array into multiple subsets and applies different read thresholds to each subset. This segmentation allows the system to account for variations in cell characteristics across different regions, improving read accuracy without requiring a completely complex individualized approach for each cell.
Solution Approach 2:
The patent implements local quality by applying different read thresholds to different subsets of memory cells based on their specific characteristics. Each subset receives a tailored read threshold that is optimized for its local variations, thereby improving overall read reliability while maintaining manageable complexity through systematic organization.
2Loss of time
If multiple sets of read thresholds are applied to different subsets simultaneously, then optimal read thresholds can be estimated with low latency, but the device complexity increases
Solution Approach 1:
The patent merges multiple read operations into a single sense operation by simultaneously applying different read thresholds to different subsets of memory cells. This combining approach allows the system to estimate optimal read thresholds for all subsets in parallel, significantly reducing the time required compared to sequential operations, while the complexity is managed through unified control mechanisms.
Solution Approach 2:
The patent introduces a new dimension to the read operation by applying multiple read thresholds simultaneously across different spatial subsets of memory cells. This dimensional expansion allows parallel evaluation of multiple threshold candidates without increasing temporal duration, effectively trading spatial complexity for temporal efficiency.
3Measurement precision
If iterative threshold adjustment is performed to improve read accuracy, then read errors are reduced, but the reading time and computational complexity increase
Solution Approach 1:
The patent performs preliminary action by estimating the optimal read thresholds in advance through a single sense operation that simultaneously evaluates multiple threshold candidates across different subsets. This preliminary estimation eliminates the need for iterative adjustments during actual read operations, thereby maintaining high read threshold accuracy while preserving fast reading speeds.
Solution Approach 2:
The system performs self-service by automatically determining the optimal read thresholds through the simultaneous multi-voltage sense operation. The memory system self-adjusts its read parameters based on the estimated optimal thresholds without requiring external iterative intervention, thus achieving both high accuracy and fast operation.
Data Source
AI summary
A method includes dividing a group of analog memory cells into multiple subsets. The memory cells in the group are sensed simultaneously by performing a single sense operation, while applying to the subsets of the memory cells respective different sets of read thresholds, so as to produce respective readout results. An optimal set of the read thresholds is estimated by processing the multiple readout results obtained from the respective subsets using the different sets of the read thresholds.