Dynamic Refresh Scheduling for Memory Cells Based on Retention Time
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Solution Overview
Problem
Conventional volatile memory devices face performance limitations due to the increasing number of memory cells with retention times shorter than the standard refresh period, necessitating a higher number of redundancy rows, which affects efficiency and power consumption.
Innovation Solution
A method is introduced where a memory system and controller dynamically manage refresh operations by grouping memory cells based on their data retention times, using a look-up table to schedule refresh requests at varying rates and temperatures, optimizing the refresh schedule to enhance performance and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the refresh period is extended to accommodate memory cells with shorter retention times, then more memory cells can be retained without redundancy, but the data retention reliability of cells with shorter retention times deteriorates
Solution Approach 1:
The patent segments memory cells into multiple groups based on their data retention times. Each group is assigned a different refresh rate, allowing cells with shorter retention times to be refreshed more frequently while cells with longer retention times are refreshed less frequently. This segmentation resolves the contradiction by enabling differentiated refresh strategies that maintain reliability for each cell type while optimizing overall memory efficiency.
Solution Approach 2:
The patent implements dynamic refresh rate adjustment where the refresh period varies depending on the retention time characteristics of different memory cell groups. Instead of using a fixed refresh period, the system dynamically adapts the refresh timing to match the specific retention requirements of each cell group, thereby maintaining data reliability while improving overall memory utilization.
2Reliability
If the number of redundancy rows is increased to accommodate memory cells with shorter retention times, then data retention reliability improves, but device complexity and power consumption increase
Solution Approach 1:
The patent segments memory cells into multiple groups based on their data retention times. Each group is assigned a different refresh rate, allowing cells with shorter retention times to be refreshed more frequently while cells with longer retention times are refreshed less frequently. This segmentation resolves the contradiction by enabling differentiated refresh strategies that maintain reliability for each cell type while optimizing overall memory efficiency.
Solution Approach 2:
The patent changes the refresh rate parameter dynamically based on the retention time characteristics of different memory cell groups. By adjusting the refresh rate parameter rather than increasing redundancy rows, the system maintains data retention reliability while avoiding the increased device complexity and power consumption associated with additional redundancy structures.
3Reliability
If the number of redundancy rows is increased to accommodate memory cells with shorter retention times, then data retention reliability improves, but power consumption increases
Solution Approach 1:
The patent segments memory cells into multiple groups based on their data retention times. Each group is assigned a different refresh rate, allowing cells with shorter retention times to be refreshed more frequently while cells with longer retention times are refreshed less frequently. This segmentation resolves the contradiction by enabling differentiated refresh strategies that maintain reliability for each cell type while optimizing overall memory efficiency.
Solution Approach 2:
The patent changes the refresh rate parameter dynamically based on the retention time characteristics of different memory cell groups. By adjusting the refresh rate parameter rather than increasing redundancy rows, the system maintains data retention reliability while avoiding the increased power consumption associated with additional redundancy structures and operations.
4Reliability
If refresh operations are performed at a fixed high rate for all memory cells, then data retention reliability improves, but productivity and power efficiency deteriorate
Solution Approach 1:
The patent segments memory cells into multiple groups based on their data retention times. Each group is assigned a different refresh rate, allowing cells with shorter retention times to be refreshed more frequently while cells with longer retention times are refreshed less frequently. This segmentation resolves the contradiction by enabling differentiated refresh strategies that maintain reliability for each cell type while optimizing overall memory efficiency.
Solution Approach 2:
The patent implements dynamic refresh rate adjustment where the refresh period varies depending on the retention time characteristics of different memory cell groups. Instead of using a fixed refresh period, the system dynamically adapts the refresh timing to match the specific retention requirements of each cell group, thereby maintaining data reliability while improving overall memory utilization.
Data Source
AI summary
A memory system includes at least one memory device and a memory controller. The at least one memory device includes a refresh request circuit that generates refresh request signals at timings based on data retention times of memory cells, such as based on individual data retention times of a memory cell row. The memory controller schedules operation commands for the at least one memory device in response to the received refresh request signals.