Memory System Word Line Active Duration Measurement and Refresh Control
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Solution Overview
Problem
Memory cells experience data loss due to word line disturbance caused by current leakage and charge fluctuations, leading to increased probability of data loss as the activity of an activated word line increases.
Innovation Solution
A memory system that includes a measurement block to detect the active duration of word lines and a refresh circuit to control a refresh operation for adjacent word lines when the active duration exceeds a threshold, thereby preventing data loss by sequentially refreshing adjacent word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the active word line remains activated for a long time to maintain data access, then data accessibility is improved, but word line disturbance increases causing data loss in adjacent memory cells
Solution Approach 1:
The patent performs refresh operations on adjacent word lines before data loss occurs due to disturbance. The measurement block detects when an active word line has been activated for a predetermined period, and the refresh circuit proactively refreshes adjacent word lines in advance, preventing data loss before it happens.
Solution Approach 2:
The patent implements a feedback mechanism where the measurement block continuously monitors the active duration of word lines and provides this information to the refresh circuit. Based on this feedback about how long a word line has been active, the system dynamically determines when to perform refresh operations on adjacent word lines.
2Reliability
If refresh operations are performed frequently on adjacent word lines to prevent data loss, then data integrity is improved, but system performance and productivity deteriorate due to increased refresh overhead
Solution Approach 1:
The patent changes the parameter of refresh timing from fixed periodic intervals to dynamic intervals based on actual word line activation duration. The measurement block measures the actual active duration, and the refresh circuit performs refresh operations only when this measured duration exceeds a predetermined threshold, optimizing refresh frequency based on actual system conditions.
Solution Approach 2:
The patent performs refresh operations selectively on only those adjacent word lines that are at risk of disturbance, rather than refreshing all word lines uniformly. This partial action approach refreshes only the necessary word lines based on the active duration of the current active word line, reducing unnecessary refresh overhead.
Data Source
AI summary
A memory includes a plurality of word lines, a measurement block suitable for measuring an active duration of an activated word line among the multiple word lines, and a refresh circuit suitable for controlling a refresh operation to refresh one or more of the multiple word lines adjacent to the activated word line when the active duration exceeds a predetermined threshold.