Targeted Refresh Control for DRAM Power and Reliability
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Solution Overview
Problem
Memory cells experience data loss due to charge leakage and word line disturbances, particularly when highly active word lines are excessively activated, leading to inefficient refresh operations and increased power consumption.
Innovation Solution
A memory system that includes a refresh control unit to periodically activate a refresh signal, a target refresh control section to selectively refresh word lines adjacent to highly active word lines, and an address detection unit to identify and manage word lines based on activation frequency and number, thereby reducing unnecessary refresh operations and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all word lines are refreshed periodically to prevent data loss, then data reliability is improved, but power consumption increases
Solution Approach 1:
The patent applies local quality by differentiating refresh operations between highly active word lines and normal word lines. Highly active word lines undergo target refresh operations that include adjacent word line refreshing to prevent disturbance effects, while normal word lines undergo standard refresh operations. This localized differentiation ensures data reliability for critical word lines without unnecessarily consuming power across all word lines.
Solution Approach 2:
The patent implements partial action by performing refresh operations only on word lines that require them based on activation frequency thresholds. Instead of refreshing all word lines uniformly, the system identifies highly active word lines through the address detection unit and applies enhanced refresh operations selectively, reducing overall power consumption while maintaining data reliability where needed.
2Reliability
If refresh operations are performed on all word lines, then data loss prevention is improved, but refresh operation efficiency deteriorates
Solution Approach 1:
The patent segments the refresh operation into two distinct types: target refresh operations for highly active word lines and normal refresh operations for other word lines. The refresh control unit manages these segmented operations differently, with target refresh operations including additional adjacent word line refreshing to prevent disturbance effects. This segmentation improves refresh operation efficiency by avoiding unnecessary comprehensive refreshes while maintaining data loss prevention for critical word lines.
Solution Approach 2:
The patent applies partial action by performing enhanced target refresh operations only on highly active word lines that are susceptible to disturbance effects, rather than applying the same enhanced operations to all word lines. The address detection unit identifies which word lines require target refresh operations based on activation frequency, enabling the system to perform partial refresh operations that improve efficiency while maintaining data loss prevention where necessary.
3Reliability
If target refresh operations are performed frequently on highly active word lines, then data loss prevention is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamics by making the refresh operation frequency and type adaptive based on real-time word line activation patterns. The address detection unit continuously monitors activation frequencies, and the refresh control unit dynamically adjusts which word lines receive target refresh operations versus normal refresh operations. This dynamic adaptation prevents excessive power consumption on word lines that become less active, while maintaining enhanced protection for consistently highly active word lines.
Solution Approach 2:
The patent employs feedback through the address detection unit that monitors word line activation frequencies and provides information to the refresh control unit. This feedback mechanism enables the system to adjust refresh operations based on actual usage patterns, performing target refresh operations only on word lines that demonstrate high activation frequency and susceptibility to disturbance effects, thereby optimizing the balance between data loss prevention and power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents data loss in memory cells adjacent to highly active word lines by targeted refresh operations and minimizes power consumption by reducing the frequency of refresh operations when word lines are not highly active.
Implementation Method 1
a capacitor that stores a charge (data)
Implementation Method 2
the initial charge stored in the capacitor is reduced due to current leakage at the PN junction
Implementation Method 3
electromagnetic waves generated in the toggling of the word line between the activated state and the precharged state causes the transfer of electrons to/from electrically coupled memory cell capacitors
Data Source
AI summary
A memory includes a plurality of word lines, a target address generation unit generating one or more target addresses by using a stored address, a refresh control section activating a refresh signal in response to a refresh command that is periodically inputted and periodically activating the refresh signal in a self-refresh mode, a target refresh control section activating a target refresh signal when the refresh signal is activated M times, wherein the M is a natural number, and deactivating the target refresh signal in the self-refresh mode, and a row control section sequentially refresh a plurality of first word lines in response to the refresh signal and refreshing a second word line corresponding to the target address in response to the refresh signal when the target refresh signal is activated.