Memory Read Calibration Using PEC Range Segmentation
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Solution Overview
Problem
Existing memory systems face challenges in maintaining accurate read calibration across different ranges of program/erase cycles (PECs), leading to disconnects between wear leveling windows and trim modulation frequencies, which complicates media management and data retention.
Innovation Solution
The implementation of a calibration method that adjusts read levels based on the quantity of PECs undergone by memory cells, allowing for media management operations to be performed using specific trims corresponding to different ranges of PECs, thereby mitigating disconnects and improving data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single trim is used for all memory cells regardless of PEC range, then device complexity is reduced, but measurement precision of read calibration deteriorates
Solution Approach 1:
The patent segments memory cells into different groups based on their program/erase cycle (PEC) ranges. Each group is assigned a specific trim value that is optimized for its wear level. This segmentation allows the system to maintain high read calibration accuracy for each group while managing complexity through organized grouping strategies.
Solution Approach 2:
The patent implements dynamic trim adjustment where trim values are not fixed but are selected based on the current PEC range of memory cells. This dynamic approach allows the system to adapt trim settings to the actual wear state of memory cells, maintaining measurement precision without requiring a completely static complex calibration system.
2Productivity
If wear leveling windows are made larger to reduce calibration frequency, then productivity is improved, but measurement precision of read calibration deteriorates
Solution Approach 1:
The patent divides the wear leveling process into smaller PEC range windows rather than using large windows. This segmentation allows calibration to be performed more frequently at appropriate intervals, maintaining read calibration accuracy while still improving overall productivity compared to traditional single-window approaches.
Solution Approach 2:
The patent implements periodic calibration operations at specific PEC thresholds within each wear leveling window. Instead of calibrating continuously or only at window boundaries, the system performs calibration at optimized periodic intervals based on PEC accumulation, balancing productivity gains with maintained measurement precision.
3Measurement precision
If trim modulation frequency is increased to improve read calibration, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the trim modulation process by associating specific trim values with specific PEC ranges. This segmentation reduces the complexity of trim modulation management by organizing trims into discrete groups rather than requiring continuous complex modulation, while still achieving improved measurement precision through range-specific optimization.
Solution Approach 2:
The patent changes trim parameters based on PEC range thresholds. Instead of complex continuous modulation, the system adjusts discrete trim parameters at defined PEC milestones, simplifying the management of trim modulation while maintaining improved read calibration accuracy through parameter adaptation.
Data Source
AI summary
A signal associated with performance of a memory operation can be applied to a memory cell of a first group of memory cells that have undergone PECs within a first range. The signal can have a first magnitude corresponding to a second range of PECs. Whether differences between a first target voltage and the signal and between a second target voltage and the applied signal are at least the threshold value can be determined. Responsive to determining that the differences are at least the threshold value, the first group of memory cells can be associated with a first calibration cluster and the signal having a second magnitude corresponding to a third range of PECs can be applied to a memory cell of a second group of memory cells that have undergone respective quantities of PECs within the second range.