Memory Read Threshold Selection Using Component-Code Scores
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Solution Overview
Problem
Existing memory devices face challenges in setting accurate reading-thresholds for analog memory cells, especially when the threshold-voltage distributions drift or become distorted due to extensive usage or environmental factors, leading to decoding failures when using multi-component error correction codes.
Innovation Solution
A system and method that calculates component-code scores for multiple threshold settings, selects the best setting based on these scores to achieve optimal readout performance, and updates the thresholds to refine the positioning for better data retrieval, even at low signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional reading-threshold setting methods are used, then the readout process is simple and fast, but the bit error rate increases when threshold-voltage distributions drift or distort
Solution Approach 1:
The patent performs preliminary actions by calculating component-code scores for multiple candidate threshold settings before actual data retrieval. This advance evaluation identifies the optimal threshold setting that will minimize bit errors, allowing the system to prepare the best reading configuration in advance rather than using fixed or simple adaptive thresholds.
Solution Approach 2:
The patent implements feedback by using calculated component-code scores to evaluate and compare different threshold settings. The system feeds back this performance information to select the threshold setting with the highest score, creating a closed-loop system that continuously optimizes reading thresholds based on actual code performance rather than relying on predetermined values.
2Measurement precision
If multiple threshold settings are evaluated to find the optimal one, then readout accuracy improves, but the time required for threshold selection increases
Solution Approach 1:
The patent changes the evaluation parameter from simple error counting to component-code scoring, which provides a more nuanced and accurate measure of threshold quality. This scoring mechanism evaluates multiple aspects of code performance simultaneously, enabling faster identification of the optimal threshold setting without requiring exhaustive testing of all possible thresholds.
Solution Approach 2:
The patent applies partial action by evaluating a limited set of candidate threshold settings rather than exhaustively testing all possible thresholds. The component-code score calculation efficiently ranks these candidates, allowing the system to achieve high accuracy by evaluating only the most promising options rather than all possible threshold combinations.
3Reliability
If component-code scores are calculated for all threshold settings, then the best threshold setting can be selected, but the computational complexity increases
Solution Approach 1:
The patent segments the error correction process into multiple component codes, each evaluated independently with its own score. This segmentation allows the system to assess the performance contribution of each component code separately, making the overall evaluation more manageable and computationally efficient while maintaining high readout performance through selective threshold selection.
Data Source
AI summary
A storage device includes a memory that includes storage circuitry and a memory including multiple memory cells. The storage circuitry is configured to store in a group of the memory cells data that was encoded using an error correcting code (ECC) consisting of multiple component codes, to define multiple threshold settings, each specifying positions of one or more reading-thresholds, to read the data from the memory cells in the group using the threshold settings and decode the read data using the component codes, to calculate for the component codes respective component-code scores that are indicative of levels of confidence in the decoded data of the component-codes, to select, based on the component-code scores, a threshold setting that is expected to result in a best readout performance among the multiple threshold settings, and to read data from the memory using the selected threshold setting.