Bank-Level Self-Refresh to Limit Memory Peak Current
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Solution Overview
Problem
Increasing memory density in electronic devices leads to higher power distribution network (PDN) requirements, resulting in increased fabrication costs and peak current demands, which are not efficiently managed by existing all-bank refresh operations.
Innovation Solution
Implementing bank-level self-refresh techniques that iteratively perform self-refresh operations on subsets of memory banks, reducing peak current and PDN requirements by staggering refresh operations across different sets of banks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all-bank refresh operations are performed simultaneously, then data integrity is maintained across all memory banks, but peak current demands and PDN requirements increase significantly
Solution Approach 1:
The memory system is divided into multiple banks that can be refreshed independently. The refresh controller segments the refresh operations by selecting specific banks to refresh in each refresh cycle, rather than refreshing all banks simultaneously. This segmentation allows the system to maintain data integrity across all banks while limiting the peak current drawn from the PDN at any given time.
Solution Approach 2:
The system implements periodic refresh operations where different sets of banks are selected for refreshing in alternating refresh cycles. The refresh controller uses a bank set indicator and counter to systematically cycle through different bank combinations, ensuring that all banks receive periodic refresh attention while distributing the power demand over time rather than concentrating it in a single simultaneous operation.
2Reliability
If all-bank refresh operations are performed simultaneously, then complete memory coverage is achieved, but fabrication costs increase due to higher PDN requirements
Solution Approach 1:
By segmenting the memory into independently refreshable banks and implementing a selective refresh scheme, the PDN can be designed with lower current capacity requirements. This reduces the complexity and cost of manufacturing the power distribution network, as fewer and smaller power delivery structures are needed compared to a system that refreshes all banks simultaneously.
Solution Approach 2:
The system performs partial refresh operations on subsets of banks in each cycle rather than excessive simultaneous refresh of all banks. The bank set indicator and counter mechanism ensures that over multiple cycles, all banks receive adequate refresh coverage, but each individual operation involves only a portion of the total banks, reducing PDN requirements and manufacturing complexity.
3Reliability
If all-bank refresh operations are performed simultaneously, then refresh completeness is ensured, but data transfer latency increases
Solution Approach 1:
The refresh operations are segmented into multiple independent bank sets that can be processed in parallel or alternating fashion. The refresh controller manages multiple bank sets with associated counters, allowing different bank sets to be refreshed in different cycles without blocking each other. This segmentation reduces the time any single bank set needs to wait for refresh completion, thereby reducing overall data transfer latency.
Solution Approach 2:
The system maintains continuous useful action by ensuring that while one set of banks is being refreshed, other bank sets remain available for data operations. The alternating refresh scheme ensures that refresh operations are continuously performed on different banks without creating long idle periods where no useful work is being done, thus minimizing the impact on data transfer latency.
Data Source
AI summary
Described apparatuses and methods relate to a bank-level self-refresh for a memory system. A memory device can include a controller with logic that implements self-refresh operations in the memory device. The logic may perform self-refresh operations on a set of banks of the memory device that is less than all banks within the memory device. The set of banks of the memory device may be determined such that the peak current in a power distribution network of the memory device is bounded when the self-refresh operation is performed. Accordingly, bank-level self-refresh can reduce a cost of the memory device of a memory system by enabling use of a less complicated power distribution network. The bank-level self-refresh may also be implemented with different types of refresh operations. Amongst other scenarios, bank-level self-refresh can be deployed in memory-expansion environments.