Storage Device Parallel Scan Refresh Control
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Solution Overview
Problem
Existing storage devices face challenges in efficiently performing scan operations to detect data deterioration in memory blocks, which affects the timely execution of refresh operations.
Innovation Solution
The proposed solution involves a storage device with a memory block comprising multiple strings of memory cells, where a threshold voltage detecting operation is performed by simultaneously applying detecting voltages to word lines. The memory controller receives read data from this operation, determines the number of strings with lower threshold voltages, and decides whether to perform a refresh operation based on this data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scan operation is performed to detect data deterioration in memory blocks, then data integrity is maintained, but the operation consumes significant time
Solution Approach 1:
The memory block is divided into multiple strings, and the scan operation processes these strings in parallel by simultaneously applying detecting voltages to multiple word lines. This segmentation allows the scan operation to detect threshold voltage distributions across all strings concurrently, significantly reducing the total scan time while maintaining comprehensive data integrity monitoring.
Solution Approach 2:
The patent performs a threshold voltage detecting operation as a preliminary scan operation before full refresh operations are needed. By detecting the threshold voltage distribution of strings in advance and identifying strings with voltages below a reference level, the system can proactively determine which strings require refresh, reducing the overall time needed for data integrity maintenance.
2Reliability
If a refresh operation is performed on the memory block, then data deterioration is prevented, but the operation increases power consumption
Solution Approach 1:
Instead of performing refresh operations on the entire memory block, the patent applies refresh operations selectively to only those strings whose threshold voltages fall below the reference voltage during the scan operation. This localized approach ensures data retention for affected strings while avoiding unnecessary power consumption from refreshing strings that do not require it.
Solution Approach 2:
The patent performs a partial scan operation that detects threshold voltages of all strings but performs refresh operations on only a subset of strings that meet the refresh condition (threshold voltage below reference). This partial action approach maintains data reliability for strings that need refresh while minimizing the energy expenditure associated with refreshing all strings.
Data Source
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AI summary
A storage device may include a memory device including a memory block including a plurality of strings each including a plurality of memory cells and configured to perform a threshold voltage detecting operation of detecting a threshold voltage corresponding to each of the plurality of strings by simultaneously applying a detecting voltage to a plurality of word lines coupled to the plurality of memory cells, and a memory controller configured to receive read data read by the threshold voltage detecting operation from the memory device, to determine a number of strings having a lower threshold voltage than the detecting voltage on the basis of the read data, and to determine whether to perform a refresh operation on the memory block based on the determined number of strings.