Storage Controller Read Voltage Optimization
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Solution Overview
Problem
Memory devices experience performance degradation due to factors like increased retention time and program/erase cycles, leading to decreased read margins and data reliability, especially as integration levels rise, causing issues with read operations.
Innovation Solution
A storage device system that includes a first memory device and a second memory device, where the second device stores degradation information, allowing the controller to calculate optimal read voltages based on estimated degradation levels, thereby adjusting read operations to maintain data reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read operations are performed using fixed read voltage, then device complexity is reduced, but read reliability deteriorates due to performance degradation from increased retention time and P/E cycles
Solution Approach 1:
The system performs preliminary read operations to acquire degradation information about memory blocks before actual read operations. This preliminary characterization allows the system to pre-determine optimal read voltages for different memory blocks, enabling reliable reads without real-time complex adjustments during actual data access.
Solution Approach 2:
The system applies different read voltages to different memory blocks based on their individual degradation characteristics. Instead of using a uniform read voltage for all blocks, each block receives a customized read voltage tailored to its specific degradation level, thereby optimizing read reliability for each local region.
2Reliability
If read voltage is adjusted for each memory block based on degradation information, then read reliability is improved, but device complexity increases due to additional voltage calculation and management
Solution Approach 1:
The system performs read operations on memory blocks to self-acquire degradation information, then uses this information to self-determine optimal read voltages. The memory device essentially characterizes itself and adjusts its own operating parameters without requiring external intervention or complex external control systems.
Solution Approach 2:
The system uses degradation information obtained from read operations as feedback to adjust read voltages for subsequent operations. This feedback loop allows the system to continuously optimize read voltages based on actual memory block conditions, improving reliability while managing complexity through iterative refinement.
3Reliability
If conventional read operations are used without degradation compensation, then ease of operation is maintained, but data reliability deteriorates due to decreasing read margins
Solution Approach 1:
The system performs preliminary operations to acquire degradation information and calculate optimal read voltages before actual data read operations. This preliminary characterization enables the system to maintain ease of operation during actual data access while ensuring high data reliability through pre-optimized read voltages.
Data Source
AI summary
A storage device includes a first memory device including a plurality of memory blocks, and a plurality of pages included in each of the plurality of memory blocks, a second memory device configured to store first degradation information of the first memory device, and a controller configured to perform a first read operation on the first memory device using a first read voltage, to acquire the first degradation information, and to perform a second read operation on the first memory device using a second read voltage. The second read voltage is calculated using second degradation information of the first memory device estimated using the first degradation information. Each of the first degradation information and the second degradation information includes the number of error bits of each of the plurality of pages.