Dynamic Bit-Error-Rate Estimation Scan Offset Adjustment
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Solution Overview
Problem
Existing data storage devices using multi-level cells face challenges in accurately determining the bit-error-rate due to variations in threshold voltage caused by process variations, data retention issues, and program disturb conditions, leading to insufficient coverage in bit-error-rate estimation scans and increased failure rates.
Innovation Solution
Implementing a dynamic bit-error-rate estimation scan (BES) with adjustable offsets to identify pages with digital-to-analog conversion shifts, applying a second BES with an updated offset for pages exceeding a criterion, thereby enhancing scan coverage and reducing failure rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed offset is used in bit-error-rate estimation scan, then the device complexity is reduced, but the scan coverage is insufficient and measurement precision deteriorates
Solution Approach 1:
The patent implements dynamic offset adjustment in the bit-error-rate estimation scan mechanism. Instead of using a fixed offset, the system dynamically determines optimal offsets based on actual memory cell characteristics and error patterns. This allows the BES to adapt to varying conditions such as process variations, data retention issues, and program disturb conditions, thereby improving measurement precision without requiring overly complex fixed-structure mechanisms
Solution Approach 2:
The patent changes the offset parameter dynamically during the bit-error-rate estimation scan. By adjusting the offset parameter based on observed error rates and memory cell states, the system achieves better scan coverage and measurement accuracy. This parameter adaptation allows the same BES mechanism to handle diverse memory conditions effectively
2Reliability
If the BES scan range is limited, then the device complexity is reduced, but the scan coverage is insufficient leading to increased failure rates
Solution Approach 1:
The patent implements dynamic expansion of the BES scan range based on detected error patterns. When errors are detected within the initial scan range, the system dynamically extends the scan to adjacent pages or broader ranges. This dynamic approach ensures comprehensive error detection and improved reliability while avoiding the need for a permanently complex,全覆盖 scan mechanism that would be required if all possible ranges were scanned statically
Solution Approach 2:
The patent performs preliminary bit-error-rate estimation scans on a limited initial range to identify error patterns early. Based on these preliminary results, the system then determines whether expanded scanning is necessary. This preliminary action approach allows the system to maintain low complexity when errors are absent while enabling comprehensive scanning when needed, thus improving reliability without always requiring complex mechanisms
Data Source
AI summary
A sensed read threshold voltage can sometimes vary from a write threshold voltage due to one or more factors, such as data retention issues and program disturb conditions. A bit-error-rate estimation scan (BES) can be used to calibrate and optimize read thresholds in this situation. However, as more wordlines are introduced, BES may not provide suitable calibration. In such situations, the BES can be re-performed on certain pages using an additional offset.