Memory Read Threshold Control Using Fail Bit and Queue Feedback
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Solution Overview
Problem
Existing memory systems face challenges in optimizing read threshold voltages due to shifting threshold voltages caused by operating conditions such as endurance, data retention, and read disturbance, leading to read errors and performance degradation, which are difficult to manually manage.
Innovation Solution
A deep learning-based system that determines whether to change the read threshold voltage based on error information and queue utilization, calculating an optimal read threshold voltage with the lowest fail bit counts among multiple retry threshold voltages to minimize read errors and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual management of read threshold voltages is used, then device complexity is reduced, but read errors increase due to shifting threshold voltages caused by operating conditions
Solution Approach 1:
The system automatically monitors operating conditions (endurance, data retention, read disturbance) and adjusts read threshold voltages without manual intervention. The controller dynamically determines optimal read threshold voltages based on current operating conditions, allowing the system to self-manage threshold voltage optimization and reduce read errors.
Solution Approach 2:
The system continuously monitors operating conditions and uses this feedback to adjust read threshold voltages. By tracking changes in endurance, data retention, and read disturbance, the controller can dynamically optimize read thresholds, creating a closed-loop system that adapts to changing conditions and maintains high reliability.
2Reliability
If read threshold voltage is dynamically adjusted based on operating conditions, then read error rate decreases, but system complexity increases
Solution Approach 1:
The controller performs multiple functions: it monitors operating conditions (endurance, data retention, read disturbance), determines optimal read threshold voltages, and adjusts thresholds dynamically. By consolidating these functions in a single controller, the system achieves high read operation reliability without proportionally increasing overall system complexity.
3Reliability
If multiple read threshold voltages are tested to find optimal threshold, then read error rate decreases, but read latency increases
Solution Approach 1:
The system proactively monitors operating conditions and determines optimal read threshold voltages before read operations are performed. By anticipating threshold voltage shifts due to endurance, data retention, and read disturbance, the controller can pre-adjust thresholds, reducing the need for multiple threshold tests during actual read operations and minimizing read latency.
Data Source
AI summary
A controller determines whether or not a read threshold voltage, other than a history read threshold voltage being a read threshold voltage that was used in previously successful read operation, is to be used for a next read operation, based on a fail bit count associated with the read operation, an error correction capability of a decoder and utilization of a queue in the decoder. When it is determined that the history read threshold voltage is not to be used for the next read operation, the controller determines fail bit counts associated with read operations on memory cells of a memory device using read threshold voltages. The controller determines an optimal read threshold voltage based on the fail bit counts. The controller transmits, to the memory device, a first command including a parameter associated with setting the optimal read threshold voltage.