DRAM Target Refresh Control for Row Hammer Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The row hammer phenomenon in DRAM occurs when data is lost in memory cells adjacent to a specific word line due to repeated active operations, leading to data retention issues.
Innovation Solution
An electronic device with a count signal generation circuit that increases weak cell and active count signals by comparing weak cell addresses with adjacent addresses during active operations, and a target refresh control circuit that latches these addresses for targeted refresh operations to reduce 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 refresh operations selectively on adjacent word lines only when weak cells are detected. This targeted approach reduces unnecessary refresh operations while maintaining data retention protection where needed most.
Solution Approach 2:
The patent performs preliminary detection of weak cells and identification of adjacent word lines before executing refresh operations. The count signal generation circuit preemptively identifies which word lines need refresh protection, allowing the refresh control circuit to prepare and execute targeted refresh operations efficiently.
2Reliability
If weak cells are monitored and targeted refresh operations are performed, then data loss is reduced, but the measurement and detection complexity increases
Solution Approach 1:
The patent uses address copying and comparison mechanisms where the count signal generation circuit creates a copy of the weak cell address and compares it with adjacent addresses generated from the row address. This copying approach simplifies the detection process by using address manipulation rather than direct physical measurement of cell strength.
Solution Approach 2:
The patent implements feedback through the count signal generation circuit that continuously monitors active operations and updates count signals based on whether weak cells are adjacent to activated word lines. This feedback mechanism automatically adjusts refresh operation timing and targeting based on real-time operation patterns.
3Reliability
If refresh operations are performed more frequently, then the row hammer effect is reduced, but the loss of time increases
Solution Approach 1:
The patent applies partial action by performing refresh operations only on the subset of adjacent word lines that are actually adjacent to weak cells, rather than refreshing all adjacent word lines uniformly. This selective partial refresh reduces the total time spent on refresh operations while maintaining effective protection against row hammer effects.
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.