Weak-Cell-Aware DRAM Refresh Control for Row Hammer Mitigation
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Solution Overview
Problem
The row hammer phenomenon in DRAM devices, where data loss occurs in memory cells adjacent to a specific word line due to repeated active operations, is not effectively addressed by existing technologies.
Innovation Solution
An electronic device with a count signal generation circuit that compares weak cell addresses with adjacent addresses during active operations, and a target refresh control circuit that latches and outputs these addresses for targeted refresh operations based on count signals, thereby reducing the row hammer effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a refresh operation is performed on all adjacent word lines, then the row hammer phenomenon is reduced, but the device complexity and operation time increase
Solution Approach 1:
The patent applies local quality by differentiating between weak cells and normal cells, and by performing targeted refresh operations only on specific adjacent word lines where weak cells are located. The count signal generation circuit identifies weak cells through comparison with adjacent addresses, and the target refresh control circuit generates refresh signals only for affected areas, rather than uniformly refreshing the entire memory array. This localized approach maintains data retention reliability while reducing overall operational complexity.
Solution Approach 2:
The patent implements feedback through the count signal generation circuit that continuously monitors and counts active operations on word lines adjacent to weak cells. When the count exceeds a threshold, the target refresh control circuit triggers a refresh operation. This closed-loop feedback mechanism ensures refresh operations are performed only when necessary, optimizing between data retention and operational efficiency.
2Reliability
If refresh operations are performed frequently, then data loss from row hammer is reduced, but the duration of active operations increases
Solution Approach 1:
The count signal generation circuit provides feedback by monitoring the number of active operations on adjacent word lines and triggering refresh operations only when the count exceeds a predetermined threshold. This prevents unnecessary frequent refresh operations while ensuring data retention, thereby optimizing the duration of active operations.
Solution Approach 2:
The system performs preliminary identification of weak cells and their adjacent word lines before actual data loss occurs. By pre-positioning the refresh control circuit to target specific areas, the system can perform refresh operations more efficiently when needed, reducing the overall duration of active operations compared to reactive approaches.
3Reliability
If targeted refresh operations are performed only on weak cell adjacent word lines, then the row hammer effect is reduced, but the measurement precision of which word lines need refresh decreases
Solution Approach 1:
The count signal generation circuit continuously monitors active operations and provides real-time feedback on which word lines are being repeatedly accessed. This feedback mechanism enables precise identification of affected word lines, ensuring that refresh operations are targeted accurately at the correct locations without losing measurement precision.
Solution Approach 2:
The patent replaces complex mechanical address comparison mechanisms with an electronic counting and comparison system. The count signal generation circuit electronically compares weak cell addresses with adjacent addresses and counts active operations, providing precise digital measurement and control of which word lines require refresh, thereby maintaining high measurement precision.
Data Source
AI summary
An electronic device includes a count signal generation circuit configured to increase one of the values of a weak cell count signal and an active count signal by comparing a weak cell address with an adjacent address generated from a row address, when an active operation is performed. The electronic device also includes a target refresh control circuit configured to latch the adjacent address based on the values of the weak cell count signal and the active count signal and to output the latched adjacent address as a target address for a refresh operation based on a target refresh signal.