Volatile Memory Refresh Leveraging Weak Cell Address
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Solution Overview
Problem
Volatile memory devices, such as DRAM, face inefficiencies in refresh operations due to the increasing number of weak cells with data retention times shorter than the standard refresh period, leading to a need for improved refresh methods that reduce the number of redundancy cells and enhance repair ratios.
Innovation Solution
A method involving the storage of address information for weak cells with shorter refresh periods, performing counting operations to generate refresh row addresses, comparing these addresses with stored information, and adjusting the refresh schedule to optimize the refresh leveraging process, thereby reducing unnecessary refresh cycles and improving repair efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the standard refresh period is used for all memory cells, then the refresh operation is simple and uniform, but weak cells with shorter data retention times cannot be properly maintained, leading to data loss
Solution Approach 1:
The refresh operation is segmented into standard refresh for normal cells and refresh leveraging for weak cells. Weak cells are identified and separated into a distinct group that requires specialized handling with shorter refresh periods, while normal cells continue to use the standard refresh period.
Solution Approach 2:
Weak cell row addresses are pre-stored in an address storing unit before the refresh operation begins. This allows the refresh controller to quickly access and identify weak cells during the refresh cycle without performing complex real-time analysis.
2Reliability
If refresh leveraging is implemented for weak cells, then data retention for weak cells is improved, but the number of refresh operations increases, reducing refresh efficiency
Solution Approach 1:
The refresh leveraging operation merges the refresh of weak cells with the standard refresh operation. By using the same refresh controller and timing infrastructure, the system performs both standard refresh and refresh leveraging in an integrated manner, reducing overhead and improving efficiency.
Solution Approach 2:
The system uses its own refresh row address counter and comparison logic to automatically identify and refresh weak cells during the standard refresh cycle, eliminating the need for separate external control mechanisms and reducing overall refresh overhead.
3Measurement precision
If weak cell row addresses are stored and compared during refresh, then refresh leveraging accuracy is improved, but the address comparison and pointer management complexity increases
Solution Approach 1:
An address storing unit acts as an intermediary between the refresh controller and the weak cell identification process. This unit stores weak cell row addresses and provides them to the comparison logic, simplifying the overall address management while maintaining high identification accuracy.
Solution Approach 2:
Instead of managing complex pointer arithmetic and address calculations during refresh, the system uses a copy of weak cell row addresses stored in the address storing unit. This allows direct comparison with the current refresh row address without complex address manipulation logic.
Data Source
AI summary
A method is provided for refreshing a volatile memory. The method includes storing address information about a weak cell row address that is to be refreshed according to a weak cell refresh period that is shorter than a refresh period, performing a counting operation for generating a refresh row address, comparing the refresh row address with the address information, refreshing the weak cell row address when a result of the comparison shows that the refresh row address and the weak cell row address of the address information coincide with each other, changing the weak cell row address by changing a pointer of the address information, and refreshing the changed weak cell row address according to the weak cell refresh period.