Adaptive Reference Voltage Update for Flash Memory Read Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Non-volatile data storage devices face accuracy issues in reading data due to variations in memory cell threshold voltages over time, leading to errors caused by factors like data retention and program disturb conditions, which existing technologies fail to adequately address.
Innovation Solution
The solution involves updating a set of reference voltages based on iterative comparisons of error counts associated with each reference voltage, alternate reference voltages, and a decreasing voltage increment to refine the selection of updated reference voltages, thereby improving data reading accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed reference voltages are used for reading data from flash memory cells, then the reading process is simple and fast, but read accuracy deteriorates over time due to threshold voltage variations
Solution Approach 1:
The patent applies dynamics by transitioning from fixed reference voltages to dynamic, adaptive reference voltages that are automatically adjusted based on observed read errors. The system monitors read accuracy over time and updates reference voltages accordingly, allowing the reading mechanism to adapt to threshold voltage variations in flash memory cells without manual intervention.
Solution Approach 2:
The patent implements feedback by establishing a closed-loop system where read errors are monitored and used to adjust reference voltages. The error correction decoder provides feedback about read accuracy, and this information is fed back to the reference voltage generation mechanism, which then modifies the reference voltages to improve future read operations.
2Reliability
If reference voltages are updated frequently to maintain read accuracy, then read error rate decreases, but processing latency increases
Solution Approach 1:
The patent applies periodic action by updating reference voltages at specific intervals or based on trigger conditions rather than continuously. The system performs read operations, monitors for errors, and updates reference voltages periodically or when error thresholds are exceeded, balancing the need for accuracy with the cost of frequent updates.
Solution Approach 2:
The patent implements self-service by enabling the system to automatically detect and correct reference voltage drift without external intervention. The error correction decoder and reference voltage generation work together to self-adjust the reference voltages based on observed read patterns, eliminating the need for manual calibration or external control.
3Reliability
If multiple alternate reference voltages are tested to optimize read accuracy, then error count decreases, but computational complexity increases
Solution Approach 1:
The patent applies partial action by testing only a limited number of alternate reference voltages (typically one or two alternatives) rather than exhaustively testing all possible voltage values. This partial search approach provides sufficient accuracy improvement while keeping the computational complexity manageable, avoiding the need to evaluate every possible reference voltage combination.
Data Source
AI summary
A method includes, in a data storage device that includes a non-volatile memory, selecting an updated reference voltage as one of a reference voltage, a first alternate reference voltage and a second alternate reference voltage. The first alternate reference voltage and the second alternate reference voltage are calculated based on the reference voltage and based on a voltage increment. Selection of the updated reference voltage is based on a comparison of error counts, each error count associated with a unique one of the reference voltage, the first alternate reference voltage, and the second alternate reference voltage. The method includes resetting the reference voltage to the updated reference voltage, resetting the voltage increment to a reset voltage increment that is smaller than the voltage increment, and selecting an additional updated reference voltage based on the reset reference voltage and based on the reset voltage increment.