Flash Memory Read Voltage Adjustment via Bit Count Feedback
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Solution Overview
Problem
Flash memory devices face issues with data reliability and speed due to variations in threshold voltage distributions over time, leading to discrepancies between programmed and read data, which existing error correction methods fail to fully address.
Innovation Solution
A method is introduced to adjust read voltages in flash memory devices by calculating and applying voltage level compensation based on differences between program and read count information, using program count information stored in spare regions to enhance data reading accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read voltages are used to read data from flash memory cells, then data can be retrieved from the memory device, but threshold voltage variations cause discrepancies between programmed and read data, reducing data reliability
Solution Approach 1:
The patent applies feedback by counting the number of bits with first logic value in both programmed data and read data, comparing these counts, and using the difference to adjust read voltages. This closed-loop feedback mechanism continuously corrects reading accuracy based on actual performance, resolving the contradiction between maintaining data reliability and ensuring precise data retrieval.
Solution Approach 2:
The patent changes the voltage parameter dynamically by adjusting read voltages based on the difference between programmed and read bit counts. This parameter adjustment compensates for threshold voltage variations, thereby improving both data reliability and reading accuracy simultaneously.
2Reliability
If traditional error correction methods are used to handle threshold voltage variations, then some errors can be corrected, but uncorrectable errors remain and data reliability is not fully improved
Solution Approach 1:
The patent performs preliminary action by storing program count information (the number of bits with first logic value) when data is programmed into the memory cells. This pre-stored information is later used to adjust read voltages before actual reading occurs, preventing uncorrectable errors rather than just correcting them, thus improving reliability without adding complex error correction mechanisms.
3Measurement precision
If read voltages are adjusted to improve data accuracy, then reading precision improves, but additional processing steps are required, potentially reducing output speed
Solution Approach 1:
The patent applies self-service by using the memory device's own programmed data to generate the correction information. The program count information is extracted from the programmed data itself, and the read voltage adjustment is automatically performed based on the comparison between programmed and read counts. This self-correcting mechanism improves reading accuracy without requiring external calibration or complex additional processing, thus maintaining output speed.
Data Source
AI summary
A method is provided for adjusting a read voltage in a flash memory device. The method includes storing first program count information when first pages of flash memory cells are programmed, the first program count information indicating a number of bits having a first logic value from among bits of data programmed in the first pages of the flash memory cells, and obtaining first read count information by counting a number of bits having the first logic value from among bits of data read from the first pages of the flash memory cells, while reading data from the flash memory cells using read voltages. The read voltages are adjusted based on the difference between the first read count information and the first program count information.