Multi-Level Cell Memory Sensing with Pre-Charge Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-level cell flash memory devices face challenges in accurately distinguishing between different states due to noise that can cause confusion, leading to unreliable performance.
Innovation Solution
A method involving sequential and concurrent sensing operations, precharging, and data transmission to reduce common source line noise, where a nonvolatile memory device performs initial and secondary sensing operations with specific read voltages and supplies pre-charge voltage to bit lines to improve read performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level cell flash memory devices store multiple bits of data per memory cell to improve storage capacity, then storage capacity is improved, but noise interference increases making it difficult to accurately distinguish between different states
Solution Approach 1:
The patent divides the read operation into multiple sequential sensing steps, where each step uses a different read voltage level to detect specific state transitions. This segmentation allows the system to distinguish between multiple data states by progressively applying voltage thresholds, thereby maintaining measurement precision while supporting high storage capacity.
Solution Approach 2:
The patent employs multiple read voltage levels (first read voltage and second read voltage) that are differentially applied during sensing operations. By changing the voltage parameter across different sensing stages, the system can accurately differentiate between various memory cell states, resolving the noise interference problem while preserving high-density storage capability.
2Measurement precision
If sequential sensing operations are performed to improve state detection accuracy, then measurement precision is improved, but read operation time increases
Solution Approach 1:
The patent applies a first read voltage to perform initial sensing operations that identify likely state transitions before applying the second read voltage. This preliminary action filters out obvious cases, allowing the second sensing operation to focus only on ambiguous states, thereby reducing overall read time while maintaining high detection accuracy.
Solution Approach 2:
The patent implements a dynamic sensing strategy where the sensing operations are performed concurrently for different bit lines when possible, and where the voltage levels are adaptively applied based on preliminary sensing results. This dynamic approach optimizes the balance between accuracy and speed by adjusting the sensing process to the actual data distribution.
3Reliability
If pre-charge voltage is supplied to bit lines to reduce common source line noise, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent supplies pre-charge voltage to bit lines before the actual sensing operation to establish a known initial state and reduce noise during the sensing process. This preliminary voltage application ensures stable sensing conditions without requiring complex noise cancellation circuits, thereby improving reliability with minimal added complexity.
Solution Approach 2:
The pre-charge voltage acts as an intermediary that prepares the bit lines for accurate sensing by eliminating common source line noise effects. Rather than making the sensing circuit itself more complex, the pre-charge mechanism serves as a simple intermediary step that enables reliable detection without additional complex components.
Data Source
AI summary
A memory system performs a first sensing operation to sense whether multi-level cells assume an on-cell state or an off-cell state in response to a first read voltage applied to a selected word line. It then supplies a pre-charge voltage to bit lines corresponding to multi-level cells that have been sensed as assuming the off-cell state in response to the first read voltage, and it performs a second sensing operation with the supplied pre-charge voltage to sense whether each of the multi-level cells that have been sensed as assuming the off-cell state assumes an on-cell state or an off-cell state in response to a second read voltage applied to the selected word line.