Flash Memory Read Voltage Calibration for Error Reduction
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Solution Overview
Problem
As flash memory integration density increases, so do operation speeds, but this also leads to higher read operation errors due to changes in threshold voltage distributions caused by environmental changes and increased program/erase cycles, affecting the reliability of flash memory systems.
Innovation Solution
A method is introduced to operate flash memory by counting memory cells within specific threshold voltage ranges and setting an optimal read voltage based on the difference between these ranges, using a reference read voltage and search read voltages with defined voltage differences, and applying an adjustment parameter to minimize read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flash memory integration density is increased to improve operation speed, then operation speed increases, but read operation errors increase due to threshold voltage distribution changes
Solution Approach 1:
The patent applies preliminary action by performing a read voltage calibration process before actual data reading operations. The memory controller pre-determines the optimal read voltage by counting threshold voltage distributions and calculating the optimal voltage that maximizes the difference between adjacent threshold voltage ranges. This preliminary calibration ensures that when read operations occur, the correct voltage is already established, preventing read errors caused by threshold voltage shifts due to environmental changes or program/erase cycles.
2Device complexity
If traditional read voltage methods are used, then device complexity remains low, but error correction time and resources increase
Solution Approach 1:
The patent performs the optimal read voltage determination in advance during a calibration phase, storing the result for use during actual read operations. This preliminary action eliminates the need for complex real-time voltage adjustments or repeated error correction attempts during data reading, significantly reducing the time and computational resources required for error correction while maintaining relatively simple device architecture.
Data Source
AI summary
A flash memory, a flash memory system, and an operating method thereof. The method of operating a flash memory includes counting the number of memory cells having threshold voltages included in a first adjacent threshold voltage range (defined by a first reference read voltage for distinguishing between initially separated adjacently located threshold voltage distributions and a first search read voltage having a first voltage difference from the first reference read voltage), and a second adjacent threshold voltage range (defined by the first reference read voltage and a second search read voltage having a second voltage difference from the first reference read voltage), and setting a first optimal read voltage based on the difference between the first and second counted numbers of the memory cells.