Nonvolatile Memory Read Operation Voltage Polarity Control
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Solution Overview
Problem
Nonvolatile memory devices face challenges in accurately reading data due to differences in charge accumulation and retention when applying positive and negative read voltages, leading to potential read operation failures.
Innovation Solution
The method involves generating distinct control signals to adjust the timing and duration of read operation intervals based on whether a positive or negative read voltage is applied, ensuring proper charge accumulation and retention on the bit line, and using operation control circuitry to manage the application of these voltages asymmetrically or symmetrically with respect to an initial word line voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single read operation interval is used for both positive and negative read voltages, then the device complexity is reduced, but the read operation accuracy deteriorates due to different charge accumulation characteristics
Solution Approach 1:
The patent implements dynamic adjustment of read operation interval parameters based on the polarity of the read voltage. The control circuitry automatically selects between first and second read operation intervals, where each interval has optimized timing characteristics tailored to either positive or negative voltage applications. This dynamic adaptation ensures accurate charge accumulation detection while maintaining systematic control.
Solution Approach 2:
The patent changes temporal parameters of the read operation interval based on voltage polarity. Specifically, the duration and timing of discharge, pre-charge, developing, and sensing intervals are adjusted according to whether a positive or negative read voltage is applied. This parameter adaptation compensates for different charge accumulation rates and retention characteristics, improving read accuracy without requiring fundamentally different circuit architectures.
2Measurement precision
If the read operation interval is extended to accommodate negative read voltage characteristics, then the charge accumulation accuracy is improved, but the read operation speed is reduced
Solution Approach 1:
The patent employs dynamic selection of read operation interval durations based on voltage polarity. For negative read voltages, a second read operation interval with extended duration is used to accommodate slower charge accumulation. For positive read voltages, a first read operation interval with shorter duration maintains faster read speeds. This dynamic timing adjustment optimizes both accuracy and speed according to operational conditions.
Solution Approach 2:
The patent adjusts the temporal parameters of the read operation interval to match the charge accumulation characteristics of each voltage type. The discharge interval, pre-charge interval, developing interval, and sensing interval are individually tuned for positive versus negative voltages. This parameter optimization ensures that each read operation uses the minimum necessary time to achieve accurate detection, preventing unnecessary delays while maintaining precision.
3Reliability
If different control signals are applied for positive and negative read voltages, then the read operation reliability is improved, but the control circuit complexity increases
Solution Approach 1:
The patent implements a universal control circuitry architecture that handles both positive and negative read voltages through a single integrated system. The control circuitry receives a read voltage polarity indicator and automatically configures the appropriate read operation interval parameters. This multi-functional approach consolidates what could be separate control paths into a unified system, improving reliability through consistent control logic while minimizing the increase in circuit complexity.
Solution Approach 2:
The control circuitry automatically detects the read voltage polarity and self-configures the appropriate read operation interval without external intervention. The system monitors the applied voltage sign and autonomously selects between the first and second read operation intervals, adjusting timing parameters as needed. This self-service capability ensures reliable operation across different voltage conditions while keeping the control logic compact and automated.
Data Source
AI summary
Within a non-volatile memory device, a read operation directed to a nonvolatile memory cell having a positive threshold voltage applies a positive read voltage to a selected word line and a first control signal to a page buffer connected to a selected bit line, but if the memory cell has a negative threshold voltage the read operation applies a negative read voltage to the selected word line and a second control signal to the page buffer different from the first control signal.