Nonvolatile Memory Read Voltage Variable Threshold Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nonvolatile memory devices rely on flag cells to indicate program states, which can lead to read errors due to charge loss and reduced data storage capacity.
Innovation Solution
A method and apparatus for a nonvolatile memory device that applies varying read voltages to determine the number of bits stored in memory cells by counting cells with threshold voltages higher or lower than the read voltage, eliminating the need for flag cells by using a counter and judge logic to compare results with reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flag cells are used to indicate program states, then read operations can be performed, but read errors occur due to charge loss and data storage capacity is reduced
Solution Approach 1:
The patent removes flag cells from the memory array by using threshold voltage distribution analysis of regular memory cells to determine program states. This extraction eliminates the source of read errors caused by flag cell charge loss while preserving data storage capacity.
Solution Approach 2:
The patent enables memory cells to self-indicate their program state through their own threshold voltage characteristics. By analyzing the threshold voltage distribution of the memory cells themselves rather than relying on separate flag cells, the system achieves self-diagnosis of program states.
2Measurement precision
If multiple read voltages are used to determine bit storage, then accuracy of bit detection is improved, but device complexity increases
Solution Approach 1:
The patent dynamically selects read voltages based on the detected program state of memory cells. Different read voltages are applied adaptively depending on whether cells are in erased or programmed states, allowing accurate bit detection while managing operational complexity through conditional logic.
Solution Approach 2:
The patent changes the read voltage parameter based on the threshold voltage distribution characteristics of the memory cells. By adjusting voltage levels according to the specific cell characteristics and program states, the system achieves accurate bit detection without requiring a fixed complex voltage scheme.
Data Source
AI summary
A method of reading a nonvolatile memory device comprises applying a read voltage to a memory cell array to read selected memory cells, counting a number of the selected memory cells that have a threshold voltage higher or lower than the read voltage, and comparing the counted number with a reference value to determine a number of bits stored in the selected memory cells.