DRAM Refresh Sequencing Reduces Address Calculator Area
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Solution Overview
Problem
In high-density DRAM structures, the address calculation for victim word lines affected by the row hammer phenomenon is complex, necessitating a larger refresh address calculator to avoid data loss due to cross-talk interference.
Innovation Solution
A memory device and refresh method that sequence-refresh redundancy and boundary word lines, eliminating the need to calculate addresses for word lines in the redundancy area, thereby reducing the area of the refresh address calculator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refresh address calculator calculates addresses for victim word lines in high-density DRAM structures, then the row hammer phenomenon can be avoided, but the area of the refresh address calculator increases
Solution Approach 1:
The patent extracts the address calculation task for redundancy word lines from the refresh address calculator. By recognizing that redundancy word lines do not require row hammer protection (as they are not adjacent to normal word lines), the calculator only processes addresses for normal and boundary word lines, thereby reducing its area while maintaining reliability.
Solution Approach 2:
The patent applies local quality by treating different word line regions differently. Normal word lines and boundary word lines require row hammer protection and are processed by the refresh address calculator, while redundancy word lines are excluded from address calculation. This localized approach reduces the calculator's workload and area requirements.
2Reliability
If the refresh address calculator processes all word lines including redundancy area, then complete refresh coverage is achieved, but the address calculation complexity increases
Solution Approach 1:
The patent extracts redundancy word lines from the address calculation process. Since these lines are not susceptible to row hammer effects, removing them from the calculator's processing scope reduces complexity while preserving necessary refresh coverage for vulnerable word lines.
Solution Approach 2:
The patent segments the memory array into normal areas and redundancy areas, and correspondingly segments the refresh process. The address calculator handles normal and boundary word lines, while redundancy word lines are refreshed separately without requiring complex address calculation, thus reducing overall system complexity.
Data Source
AI summary
A memory device and a refresh method thereof are provided. The memory device includes a memory array and a controller. The memory array includes a plurality of normal areas and a redundancy area near the plurality of normal areas. The redundancy area includes a plurality of redundancy word lines. A plurality of boundary word lines are arranged near boundaries between the plurality of normal areas and the redundancy area. The controller refreshes the plurality of redundancy word lines in sequence, and refreshes the plurality of boundary word lines in sequence after refreshing the plurality of redundancy word lines in sequence.