Memory Read Calibration via Device-Originated Voltage Metadata
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Solution Overview
Problem
Existing memory read calibration techniques are inaccurate and latency-prone, as they are 'blind' to voltage distribution shifts, leading to potential data uncorrectability and inefficiencies in non-volatile memory devices.
Innovation Solution
The use of memory device-originated metadata characterizing voltage distributions to adjust read voltage levels, minimizing latency and ensuring specified accuracy or maximizing accuracy without exceeding latency, by utilizing metadata values such as failed byte count or failed bit count to determine read voltage adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional memory read calibration techniques are used, then the read operation can be performed, but the calibration accuracy is poor and latency is high
Solution Approach 1:
The patent implements feedback by using metadata from previous read operations (such as failed byte count, failed bit count, or ECC correction information) to adjust read voltage levels in subsequent operations. This closed-loop feedback mechanism enables continuous optimization of read calibration accuracy while minimizing latency, as the system learns from actual read performance without requiring separate calibration sequences.
Solution Approach 2:
The memory device performs self-calibration by automatically adjusting its own read voltage levels based on metadata generated during normal read operations. This self-service approach eliminates the need for external calibration sequences or host intervention, thereby reducing calibration latency while maintaining high accuracy through continuous self-optimization based on actual read performance data.
2Reliability
If read voltage levels are not adjusted based on voltage distribution shifts, then read operations can proceed quickly, but data uncorrectability increases due to inaccurate calibration
Solution Approach 1:
The system uses feedback from read operations (such as ECC correction counts or failed bit indicators) to detect voltage distribution shifts and automatically adjust read voltage levels. This ensures data correctability is maintained despite voltage drift from charge loss, temperature changes, or physical defects, while avoiding the need for time-consuming explicit calibration sequences by integrating calibration into normal read operations.
Solution Approach 2:
The patent applies preliminary adjustments to read voltage levels based on metadata from previous operations, proactively compensating for voltage distribution shifts before they cause read errors. This preliminary action approach maintains data correctability by anticipating voltage drift effects without requiring reactive calibration sequences after errors occur, thereby reducing overall latency.
3Measurement precision
If metadata collection and processing is implemented for read calibration, then calibration accuracy improves, but device complexity increases
Solution Approach 1:
The memory device utilizes existing metadata that is already generated during normal read operations (such as failed byte count, failed bit count, or ECC correction information) for calibration purposes. This self-service approach repurposes existing operational data without requiring additional sensors, measurement circuits, or complex calibration hardware, thereby improving voltage distribution characterization while minimizing increases in device complexity.
Solution Approach 2:
The patent makes existing metadata serve multiple functions: it is used both for error correction during read operations and for calibrating read voltage levels. This multi-functionality approach allows the system to achieve accurate voltage distribution characterization using data already collected for other purposes, avoiding the need for dedicated calibration measurement systems and reducing overall device complexity.
Data Source
AI summary
Described are systems and methods for memory read calibration based on memory device-originated metadata characterizing voltage distributions. An example memory device comprises: a memory array comprising a plurality of memory cells electrically coupled to a plurality of wordlines; and a controller coupled to the memory array, the controller to perform operations comprising: receiving one or more metadata values characterizing threshold voltage distributions of a subset of the plurality of memory cells connected to one or more bitlines, wherein the one or more metadata values reflect a conductive state of the one or more bitlines; determining a read voltage adjustment value based on the one or more metadata values; and applying the read voltage adjustment value for reading the subset of the plurality of memory cells.