Semiconductor Memory Self-Refresh Current Reduction
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Solution Overview
Problem
Conventional semiconductor memory devices experience increased current consumption during self-refresh operations due to the selection and activation of word lines for memory cells, which is exacerbated by longer refresh cycles.
Innovation Solution
A semiconductor memory device and refresh method where banks are sequentially activated, and a word line is selected by row addresses during self-refresh operations, allowing for reduced current consumption and ensuring that all memory cells are refreshed without omitting any word lines by interrupting the self-refresh operation and performing an auto-refresh from the selected word line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If banks are simultaneously activated during self-refresh operation, then refresh coverage is ensured, but current consumption increases
Solution Approach 1:
The patent divides the bank activation process into sequential segments rather than simultaneous activation. During self-refresh operation, banks are activated one after another in a predetermined order, allowing the memory device to maintain refresh coverage across all banks while reducing the peak current consumption that would occur if all banks were activated simultaneously.
2Use of energy by moving object
If refresh cycle is extended for self-refresh mode, then power consumption is reduced, but risk of data loss increases
Solution Approach 1:
The patent implements preliminary tracking of the last accessed word line address before entering self-refresh mode. This allows the system to quickly resume and complete the refresh cycle from the correct position after exiting self-refresh, ensuring that no data is lost despite the extended refresh cycle duration inherent in self-refresh operation.
3Measurement precision
If word line selection is maintained during self-refresh, then refresh precision is improved, but current consumption increases
Solution Approach 1:
The patent applies local quality by selectively activating only the specific bank and word line that need refreshing at each moment, rather than globally activating all banks simultaneously. The sequential bank activation combined with precise word line selection based on tracked address information allows refresh precision to be maintained while significantly reducing overall current consumption.
Data Source
AI summary
A semiconductor memory device includes a memory core configured to sequentially activate first and second banks in response to first and second bank active signals which are sequentially enabled in response to first and second enable signals when a self-refresh operation is to be performed, select a word line by row addresses, and perform a refresh operation for memory cells which are connected with the word line; and an address counter configured to perform a counting operation for the row addresses in response to a counter signal, and interrupt the counting operation for the row addresses in a case where both the first and second banks are not activated when the self-refresh operation is ended.