Nonvolatile Memory Read Sequence Control for Latency Optimization
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Solution Overview
Problem
Nonvolatile memory devices face challenges in maintaining accurate read sequences due to changes in operating conditions, leading to increased read latency and performance degradation as intended threshold voltage distributions become altered or distorted by factors like charge leakage and temperature changes.
Innovation Solution
Adaptive read sequence control methods are implemented, where multiple read sequences are set and selected based on varying operating conditions, with sequence selection rates adjusted based on monitored read latencies to optimize data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed read sequence is used in nonvolatile memory devices, then the device structure and control logic are simple, but read latency increases and performance degrades when operating conditions change
Solution Approach 1:
The patent implements dynamic read sequence selection by introducing a read sequence manager that monitors operating conditions (temperature, voltage, P/E cycles) and automatically switches between multiple pre-defined read sequences. This transforms the static read control into a dynamic system that adapts to changing conditions, reducing read latency without requiring complex real-time analysis of distribution shifts.
Solution Approach 2:
The patent changes the parameter of read sequence selection from fixed to variable based on operating conditions. Multiple read sequences are pre-configured with different read voltages and timing parameters, and the system selects the appropriate sequence based on monitored parameters such as temperature, voltage levels, and program/erase cycle counts, thereby optimizing read performance without increasing fundamental system complexity.
2Reliability
If multiple read sequences are prepared to account for operating condition changes, then read performance under varying conditions improves, but device complexity and control difficulty increase
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple read sequences with optimized parameters for different operating conditions before the device operates. These sequences are prepared in advance based on anticipated conditions (temperature ranges, voltage variations, P/E cycle stages), eliminating the need for complex real-time analysis and decision-making during actual read operations.
Solution Approach 2:
The patent implements feedback mechanisms through a read sequence manager that continuously monitors operating conditions (temperature sensors, voltage detectors, P/E cycle counters) and uses this feedback to automatically select the most appropriate pre-defined read sequence. This closed-loop control simplifies management by using straightforward condition-based selection logic rather than complex adaptive algorithms.
3Productivity
If read sequences are dynamically adjusted based on monitored conditions, then read latency is reduced and performance is enhanced, but the control system becomes more complex
Solution Approach 1:
The patent segments the read control function into distinct modules: a read sequence manager, multiple pre-defined read sequences, and condition monitoring subsystems. Each module has a specific, simple function, and they work together through well-defined interfaces. This segmentation allows the system to achieve dynamic adaptation without requiring any single component to be overly complex.
Data Source
AI summary
To control a read sequence of a nonvolatile memory device, a plurality of read sequences are set and the read sequences respectively correspond to operating conditions different from each other. The read sequences are performed selectively based on sequence selection rates respectively corresponding to the read sequences. Read latencies of the respective read sequences are monitored and the sequence selection rates are adjusted based on monitoring results of the read latencies.