Flash Memory Readout Using Threshold Shift Bit Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flash memory systems face challenges in accurately reading data due to changes in threshold voltage distribution caused by factors like program/erase cycles and retention time, leading to incorrect data retrieval and uncorrectable errors.
Innovation Solution
A method and memory controller that utilize multiple read operations with different control gate voltage settings to determine binary digit distribution characteristics of bit sequences, allowing for adaptive tracking of threshold voltage distributions and correction of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If original control gate voltage settings are used to read data from flash memory cells, then the reading process is simple and fast, but the data accuracy deteriorates due to changed threshold voltage distribution from program/erase cycles and retention time
Solution Approach 1:
The patent performs preliminary read operations to obtain bit sequences before final data retrieval. These preliminary operations track the threshold voltage distribution changes and establish the binary digit distribution characteristics that guide the final accurate readout, ensuring data accuracy while managing complexity through staged processing
Solution Approach 2:
The patent implements a feedback mechanism where bit sequences obtained from preliminary read operations are analyzed to determine binary digit distribution characteristics. This feedback information is then used to adjust and optimize the reading process, ensuring accurate data retrieval despite threshold voltage distribution changes from program/erase cycles and retention time
2Measurement precision
If multiple read operations with different control gate voltage settings are performed to track threshold voltage distribution, then data reading accuracy is improved, but the reading time and operational complexity increase
Solution Approach 1:
The patent performs a limited number of read operations (exactly two read operations with different control gate voltage settings) to obtain sufficient bit sequences for tracking threshold voltage distribution. This partial action approach provides adequate measurement precision without excessive time consumption, balancing accuracy requirements with operational efficiency
Data Source
AI summary
A method for reading data stored in a flash memory includes at least the following steps: controlling the flash memory to perform a plurality of read operations upon a plurality of memory cells included in the flash memory; obtaining a plurality of bit sequences read from the memory cells, respectively, wherein the read operations read bits of a predetermined bit order from the memory cells by utilizing different control gate voltage settings; and determining readout information of the memory cells according to binary digit distribution characteristics of the bit sequences.