Memory Controller Center of Valley Read Level Adjustment
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Solution Overview
Problem
Conventional memory sub-systems face challenges in accurately correcting read errors due to inaccuracies in read levels, particularly when charges stored at one of the read levels are lost or shifted, leading to poor data recovery and failure in error correction.
Innovation Solution
A memory sub-system controller is configured to determine a correction to the read level based on a combination of criteria, using CFBit values from adjacent read levels to identify a center of valley (CoV) and ensure it is not a local minimum, thereby adjusting the read level for accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional read levels are used to read data from memory components, then data retrieval operation is simple, but read errors occur when charges are lost or shifted
Solution Approach 1:
The system performs preliminary actions by reading data at multiple adjacent read levels before determining the correct read level. It pre-calculates CFBit values and error counts for each adjacent read level, then uses this预先 obtained information to identify the center of valley and determine the accurate read level, thereby preventing read errors before they occur.
Solution Approach 2:
The system implements feedback by using the error counts and CFBit values obtained from reading at adjacent read levels to feedback into the read level determination process. The feedback mechanism identifies the center of valley based on these error metrics and adjusts the read level accordingly, creating a closed-loop system that continuously optimizes read accuracy.
2Measurement precision
If multiple adjacent read levels are read to determine CoV, then read level accuracy is improved, but number of read operations increases
Solution Approach 1:
The system applies partial action by reading data at a limited number of adjacent read levels (typically three levels: the target level and two adjacent levels) rather than exhaustively testing all possible read levels. This partial sampling provides sufficient information to identify the center of valley while minimizing the overhead of excessive read operations, thus balancing precision and productivity.
Data Source
AI summary
Aspects of the present disclosure configure a system component, such as a memory sub-system controller, to identify a center of valley (CoV) of a set of read levels. The controller detects a read error associated with reading data from the set of memory components in accordance with an individual read level of a plurality of read levels and, in response to detecting the read error, generates a plurality of bins as a function of a plurality of check failure bit count values and one or more error count values corresponding to a set of read levels adjacent to the individual read level. The controller computes the CoV for the individual read level based on a pair of read levels defined by a set of the plurality of bins and updates a read level used to read the data based on the computed CoV.