Memory Controller Read Voltage Adjustment Based on Command Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor memory devices, there is a challenge in accurately determining the optimal read voltage levels for memory cells after programming, as the threshold voltage variations can lead to read errors due to rapid charge loss immediately after programming.
Innovation Solution
A memory system with a memory controller that determines the distance between program and read commands and adjusts the read voltage level based on this distance, using a threshold value that accounts for the speed of threshold voltage variation, switching between a normal and a special read voltage level to mitigate read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed read voltage level is used for reading memory cells after programming, then the device complexity is reduced, but read errors increase due to threshold voltage variations
Solution Approach 1:
The patent applies dynamics by making the read voltage level adjustable based on the timing of read commands relative to program commands. The memory controller dynamically selects between first and second read voltage levels depending on whether the read command occurs within a threshold time period after a program command, allowing the system to adapt to threshold voltage variations without excessive complexity
Solution Approach 2:
The patent changes the read voltage parameter based on temporal conditions. By determining the distance (time interval) between program and read commands, the system selects appropriate voltage levels to compensate for threshold voltage drift, thereby maintaining read accuracy while managing device complexity
2Measurement precision
If the read voltage level is adjusted based on threshold voltage variation speed, then read accuracy is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent applies preliminary action by pre-determining threshold values that represent critical time periods for threshold voltage variation. The memory controller uses these pre-established thresholds to quickly decide which read voltage level to apply, avoiding the need for complex real-time threshold voltage measurement and adjustment mechanisms
Solution Approach 2:
The patent introduces an intermediary approach by using distance determination based on command timing rather than direct threshold voltage measurement. The controller mediates between program and read commands by calculating temporal distance and selecting voltage levels accordingly, simplifying the control mechanism while maintaining precision
3Reliability
If a higher read voltage level is always used, then read errors are reduced, but energy consumption increases
Solution Approach 1:
The patent changes the read voltage parameter dynamically based on temporal conditions. By selecting between first and second voltage levels according to the distance from the program command, the system optimizes energy consumption by using higher voltage only when necessary (within threshold time period) and lower voltage when threshold voltage variation is minimal
Data Source
AI summary
According to example embodiments, a memory system includes a memory device and a memory controller configured to control the memory device. The memory device includes a plurality of memory cells. The memory controller includes a storage unit configured to sequentially store a plurality of commands received from a host, a distance determination unit configured to determine a distance between a program command and a read command, associated with the same word line, from among the plurality of commands stored in the storage unit, and a read voltage determination unit configured to determine a read voltage level corresponding to the read command based on the determined distance.