Memory Read Disturb Scan Using Failed Bit Counts
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Solution Overview
Problem
Conventional memory systems face inefficiencies in detecting charge loss and gain in memory cells due to read disturb, requiring multiple reads and host involvement, which negatively impact system performance and quality of service.
Innovation Solution
Perform a single read disturb scan using failed bit counts to detect both charge loss and gain, eliminating the need for host involvement and reducing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reads are performed to detect charge loss and gain, then measurement precision is improved, but loss of time increases and productivity decreases
Solution Approach 1:
The patent combines multiple read operations into a single read disturb scan that simultaneously detects both charge loss and charge gain. By merging the detection of charge loss (via highest read level failed bit count) and charge gain (via lowest read level failed bit count) into one scan operation, the system achieves accurate measurement of both parameters without requiring multiple separate reads, thus reducing scan time while maintaining measurement precision.
Solution Approach 2:
The read disturb scan is designed to perform multiple functions simultaneously: it detects charge loss, detects charge gain, and identifies memory blocks requiring refresh operations. This multi-functional approach eliminates the need for separate host involvement in multiple read operations, as the single scan provides all necessary information for comprehensive memory health assessment.
2Measurement precision
If multiple reads and host involvement are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The memory device performs the read disturb scan autonomously without requiring host involvement. The controller initiates a single read disturb scan command, and the memory device independently executes the scan, collects failed bit counts for both highest and lowest read levels, and determines which blocks require refresh. This self-service approach simplifies the overall system complexity by eliminating the need for complex host-based control logic and multiple coordinated read operations.
3Reliability
If multiple reads are performed, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent merges multiple reliability-checking read operations into a single read disturb scan that simultaneously assesses memory integrity for both charge loss and charge gain conditions. This consolidation maintains comprehensive reliability monitoring while minimizing the performance impact by reducing the total number of read operations from multiple separate scans to one unified scan operation.
Data Source
AI summary
Methods, systems, and apparatuses include sending a read disturb scan command to a memory device causing the memory device to execute a first read strobe at a lowest read level of a memory portion of the memory device to determine a charge gain value for the memory portion and execute a second read strobe at a highest read level of the memory portion to determine a charge loss value for the memory portion. The charge loss value and the charge gain value are retrieved from the memory device. It is determining that a read disturb for the memory portion satisfies a read disturb threshold using the charge loss value and the charge gain value. The memory portion is flagged for refresh in response to determining that the read disturb satisfies the read disturb threshold.