Bank-Level Self-Refresh for Memory Peak Current Reduction
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Solution Overview
Problem
The increasing demand for larger and higher-density memory in electronic devices leads to higher power distribution network (PDN) requirements, resulting in increased peak currents and fabrication costs.
Innovation Solution
Implementing bank-level self-refresh techniques, where the memory device performs self-refresh operations on a subset of banks rather than all banks simultaneously, reducing peak current and corresponding PDN requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all banks perform self-refresh operations simultaneously, then data retention is maintained, but peak current increases and PDN requirements increase
Solution Approach 1:
The patent divides the memory banks into multiple groups and performs self-refresh operations on different groups at different times. Specifically, during a self-refresh period, only a first set of banks is selected to perform self-refresh operations while other banks remain inactive, thereby segmenting the simultaneous refresh operations into staggered batches that reduce peak current demands on the power distribution network
Solution Approach 2:
The patent implements periodic self-refresh operations where banks are selected in alternating patterns across different refresh cycles. A first set of banks performs self-refresh in one period while a second set performs in the next period, creating a periodic action pattern that maintains data retention across all banks while distributing the power consumption over time to reduce peak current
2Reliability
If all banks perform self-refresh operations simultaneously, then data retention is maintained, but the number of physical metal layers increases
Solution Approach 1:
The patent segments the bank refresh operations into multiple groups that operate at different times. By selecting only a first set of banks to perform self-refresh while keeping other banks inactive during each refresh period, the patent reduces the simultaneous current draw, which directly reduces the number of physical metal layers required in the power distribution network
3Reliability
If all banks perform self-refresh operations simultaneously, then data retention is maintained, but fabrication costs increase
Solution Approach 1:
The patent divides banks into multiple groups and implements staggered self-refresh operations where different groups are activated at different times. This segmentation reduces the peak current requirements, which in turn reduces the complexity of the power distribution network and the number of metal layers needed, thereby reducing fabrication costs
Solution Approach 2:
The patent changes the operational parameters of bank self-refresh by controlling the timing and selection of banks that perform refresh operations. By adjusting which banks are active during self-refresh periods and when they operate, the patent reduces peak current demands, leading to simplified PDN design and lower fabrication costs
4Reliability
If all banks perform self-refresh operations simultaneously, then data retention is maintained, but data transfer latency increases
Solution Approach 1:
The patent segments self-refresh operations into different time periods for different bank groups. During each self-refresh period, only a first set of banks is selected to perform refresh operations while other banks remain available or are refreshed in subsequent periods, reducing the overall time impact on data transfer operations compared to forcing all banks to refresh simultaneously
Data Source
AI summary
Described apparatuses and methods relate to a bank-level self-refresh for a memory system. A memory device can include 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.