Flash Memory Slicing Voltage Adjustment for Data Integrity
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Solution Overview
Problem
After repeated use, NAND-based flash memory cells experience threshold voltage shifts due to degradation, leading to increased data error rates when using fixed slicing voltages to determine storage states.
Innovation Solution
The method involves programming specific cell patterns into the flash memory to adjust the slicing voltage dynamically, allowing for accurate distinction between storage states by minimizing error percentage, utilizing a system with a scrambler, ECC encoder, cell pattern inserter, and slicing voltage adjuster to program and read data while correcting errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed slicing voltages are used to determine storage states, then the reading operation is simple and fast, but data error rate increases after repeated use due to threshold voltage shifts
Solution Approach 1:
The patent implements dynamic slicing voltage adjustment by introducing a voltage adjustment circuit that modifies the slicing voltage based on detected threshold voltage shifts. The system transitions from fixed slicing voltages to dynamically adjusted slicing voltages, allowing the reading operation to adapt to degradation and maintain low data error rates after repeated use.
Solution Approach 2:
The patent employs a feedback mechanism where the system detects threshold voltage shifts during reading operations and uses this information to adjust the slicing voltage accordingly. The voltage adjustment circuit receives feedback about threshold voltage changes and automatically compensates by modifying the slicing voltage to maintain accurate state differentiation.
2Reliability
If slicing voltage is adjusted to account for threshold voltage shifts, then data error rate decreases, but the reading operation becomes more complex
Solution Approach 1:
The patent implements a self-service mechanism where the flash memory system automatically adjusts its own slicing voltage without external intervention. The voltage adjustment circuit is integrated into the memory system, allowing it to self-correct for threshold voltage shifts and maintain reliable operation without requiring complex external control or manual calibration.
3Measurement precision
If dynamic slicing voltage adjustment is implemented, then accurate state differentiation is maintained after degradation, but device complexity increases
Solution Approach 1:
The patent changes the electrical parameter (slicing voltage) dynamically to compensate for threshold voltage shifts caused by degradation. By adjusting the slicing voltage parameter based on detected changes, the system maintains accurate state differentiation without requiring fundamental changes to the memory cell structure or reading methodology.
Data Source
AI summary
A method for determining a storing state of a flash memory is provided. The method includes the following steps. Firstly, plural first specific cell patterns are programmed into the flash memory. Then, plural second specific cell patterns are programmed into the flash memory. Then, a slicing voltage is adjusted to allow a distinguishable error percentage to be lower than a predetermined value. Afterwards, a first storing state and a second storing state of other cells of the flash memory are distinguished from each other according to the adjusted slicing voltage.