Flash Memory Sense Circuit Boost Driver Leakage Control
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Solution Overview
Problem
Flash memory devices face issues with leakage current in existing boost schemes, leading to erroneous sensing operations in flash memory devices, which affect the accuracy of read and verify operations.
Innovation Solution
A new boost scheme is implemented using a sense circuit with a boost driver, first, second, third, and fourth switches, where the boost driver outputs different voltages to manage the voltage level at a sense node, ensuring it does not exceed the system voltage, thereby eliminating leakage current and improving sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boost scheme is applied to achieve higher sensing accuracy, then sensing reliability is improved, but leakage current increases causing erroneous sensing
Solution Approach 1:
The patent applies dynamics by making the boost driver output voltage variable rather than fixed. The boost driver dynamically adjusts its output voltage based on the operating phase: outputting a first voltage during precharge, a second voltage during sensing, and a third voltage during verification. This dynamic voltage adjustment allows the system to achieve high sensing accuracy when needed while minimizing leakage current during other phases, thereby resolving the contradiction between sensing reliability and leakage current.
Solution Approach 2:
The patent changes the voltage parameter of the boost driver output across different operating phases. Specifically, it uses different voltage levels (first voltage during precharge, second voltage during sensing, third voltage during verification) to optimize performance for each phase. This parameter change approach enables the system to achieve high sensing accuracy during the sensing phase while controlling leakage current during precharge and verification phases, resolving the technical contradiction.
2Measurement precision
If the boost driver outputs high voltage continuously, then sensing accuracy is improved, but voltage level at sense node exceeds system voltage causing instability
Solution Approach 1:
The patent applies periodic action by using different voltage levels at different time periods/phases. The boost driver outputs a first voltage during precharge phase, a second voltage during sensing phase, and a third voltage during verification phase. This periodic voltage adjustment ensures that high voltage is applied only when needed for accurate sensing, while maintaining voltage level stability during other phases by using appropriate voltage levels, thus resolving the contradiction between sensing accuracy and voltage stability.
3Ease of operation
If existing boost schemes are used, then sensing operation is simplified, but leakage current causes erroneous sensing results
Solution Approach 1:
The patent implements feedback by using the sense circuit to detect the actual state of memory cells and using this information to control the boost driver output. The multi-phase voltage adjustment (first voltage during precharge, second voltage during sensing, third voltage during verification) is based on feedback from the sensing operation status. This feedback mechanism ensures accurate sensing results while maintaining operational simplicity, as the voltage adjustments are automatically controlled based on the sensing phase and detected cell states.
Data Source
AI summary
A sense circuit of a memory cell includes a first switch, a sense node, a third switch, a connection node, a fourth switch, and a memory cell coupled in series. A boost driver is coupled to the sense node. A second switch and the connection node are coupled in series. The boost driver outputs a first voltage when the first, second, third, fourth switches are turned on. The third switch is then turned off and the boost driver outputs a second voltage higher than the first voltage such that the voltage level at the sense node is not higher than a system voltage. The third switch is turned on, then turned off and the boost driver outputs an intermediate voltage between the first voltage and the second voltage. A state of the memory cell is determined during output of the intermediate voltage.