Neighbor-Aware NAND Read Timing for Higher Accuracy
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Solution Overview
Problem
Existing zoning methods in non-volatile memory apparatuses do not provide the desired read accuracy due to the influence of neighboring memory cells' data states on threshold voltages during read operations.
Innovation Solution
Implementing a dynamic look ahead (DLA) and look neighbor ahead (LNA) techniques that involve pre-reads of neighboring word lines to account for neighboring memory cells' data states, with adjusted sense times determined based on identified zones and temperature, allowing for improved read accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing zoning methods are used for read operations, then the read operation is simple and fast, but the read accuracy is insufficient due to influence from neighboring memory cells' data states
Solution Approach 1:
The patent performs pre-read operations on neighboring word lines before the actual read operation on the selected word line. This preliminary action determines the data states of neighboring memory cells in advance, allowing the system to identify which zone each memory cell belongs to and apply appropriate compensation values to adjust threshold voltages, thereby improving read accuracy while managing complexity through structured pre-processing
Solution Approach 2:
The patent divides the memory array into multiple zones based on the data states of neighboring memory cells. Each zone receives different compensation values tailored to its specific characteristics. This local differentiation allows the system to address the unique interference patterns affecting each group of memory cells, improving overall read accuracy by treating different regions with customized compensation strategies
2Measurement precision
If pre-read of neighboring word lines is performed to account for neighboring data states, then read accuracy improves, but read operation time increases
Solution Approach 1:
The patent performs pre-read operations on neighboring word lines before the actual read operation, determining data states and zones in advance. This allows compensation values to be calculated and applied beforehand, ensuring accurate threshold voltage adjustment during the main read operation without requiring iterative adjustments, thus balancing improved accuracy with acceptable time overhead
Solution Approach 2:
The patent dynamically adjusts the sense time for each memory cell based on its identified zone and the compensation values applied. The control circuit selectively extends or reduces sense time for specific zones, allowing faster reads for cells requiring minimal compensation while providing extended sense time for cells in zones with higher interference, thereby optimizing overall read performance
3Measurement precision
If adjusted sense time is used for different zones, then read accuracy improves, but the control logic becomes more complex
Solution Approach 1:
The patent implements zone-based control where each identified zone is assigned specific compensation values and sense time adjustments. The control circuit contains logic that maps memory cells to their respective zones and applies the appropriate parameters for each zone. This structured local control approach manages complexity by organizing the control logic around discrete zones rather than individual cells, making the system more tractable
Solution Approach 2:
The patent changes the sense time parameter dynamically based on the identified zone and applied compensation values. The control circuit selectively adjusts the sense time for each memory cell or zone, extending it for cells requiring stronger signal detection and using shorter times for cells with clearer signals. This parameter adaptation improves accuracy while the systematic approach to parameter selection keeps control logic manageable
Data Source
AI summary
A memory apparatus includes memory cells connected to word lines and configured to retain a threshold voltage corresponding to data states. A control means is configured to determine ones of the data states for the memory cells of a neighboring word line adjacent to a selected word line in a pre-read. The control means determines an adjusted sense time according to a zone identified for the memory cells of the neighboring word line and the one of the data states targeted for the memory cells of the selected word line and a temperature of the memory apparatus. The control means is also configured to perform reads on the selected word line for each of a plurality of groupings of ones of the data states in a read operation using the adjusted sense time determined for each of the memory cells of the selected word line.