Bank-Level Self-Refresh to Reduce Memory PDN 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 during all-bank refresh operations, which are not efficiently managed by existing memory controllers.
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 using a refresh controller and register tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all banks perform refresh operations simultaneously, then data integrity is maintained across all banks, but peak current demand and PDN requirements increase significantly
Solution Approach 1:
The patent segments the refresh operations by dividing all banks into multiple subsets (e.g., first subset and second subset). Each subset performs refresh operations at different time intervals, so that not all banks refresh simultaneously. This segmentation maintains data integrity for each subset while reducing the aggregate peak current demand on the PDN.
Solution Approach 2:
The patent implements periodic refresh operations where different bank subsets are refreshed at staggered time intervals. The refresh controller alternates between activating different subsets in a periodic manner, ensuring that each bank is refreshed within its required refresh period while spreading the current demand over time rather than concentrating it at once.
2Quantity of substance
If memory density is increased to meet growing data requirements, then storage capacity improves, but PDN requirements and fabrication costs increase
Solution Approach 1:
The patent applies segmentation to the power distribution architecture by introducing subset-specific power distribution networks or controlling mechanisms. This allows the PDN to be designed with lower peak current requirements since banks are refreshed in subsets rather than all at once, thereby reducing the complexity and cost of the power distribution infrastructure needed to support high-density memory.
3Reliability
If all banks are refreshed simultaneously, then complete data maintenance is achieved, but memory unavailability time increases
Solution Approach 1:
The patent uses periodic action to refresh different bank subsets at different times within the overall refresh period. This ensures that data maintenance is achieved for all banks over time while minimizing the duration during which any given bank is unavailable, since other banks remain accessible during their non-refresh intervals.
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.