Flash Memory Controller Voltage Distribution Adjustment
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Solution Overview
Problem
Flash memory devices, such as NAND Flash, face limitations in correcting bit errors during data storage and retrieval, as existing encoding and decoding methods are insufficient when error rates exceed a certain threshold, leading to ineffective data decoding.
Innovation Solution
A data storage device with a controller that performs a distribution-adjustment procedure by reading a second page corresponding to a different word line to adjust the threshold voltage distribution of a target page that cannot be successfully read, and a voltage-setting procedure to retry reading the target page with adjusted voltage settings, as outlined in the error correction method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional encoding and decoding methods are used to correct bit errors, then the error correction capability is limited to a certain threshold, but the system complexity remains low
Solution Approach 1:
The patent changes the voltage distribution parameters of the flash memory device by performing read operations on adjacent pages to modify the threshold voltage distribution. This allows the system to adapt to varying error conditions without adding complex hardware structures, thereby improving error correction capability while maintaining relatively simple system architecture
Solution Approach 2:
The patent performs preliminary read operations on adjacent pages before attempting to read the target page. These preliminary actions adjust the voltage distribution in advance, creating favorable conditions for successful data retrieval from the target page, thus improving reliability before the actual data reading operation
2Reliability
If voltage distribution is adjusted by reading adjacent pages, then the success rate of reading corrupted pages increases, but the reading time and operational complexity increase
Solution Approach 1:
The patent performs read operations on a limited number of adjacent pages (partial action) rather than all possible pages, which is sufficient to achieve the desired voltage distribution adjustment without excessive time consumption. This balanced approach improves reading success rate while controlling the time overhead
Solution Approach 2:
The system implements a feedback mechanism where the controller monitors the results of read operations and determines whether voltage distribution adjustment is needed. Based on this feedback, it selectively performs additional read operations on adjacent pages only when necessary, thereby improving reliability while minimizing unnecessary time consumption
Data Source
AI summary
The present invention provides a data storage device including a flash memory and a controller. The controller is configured to perform a first read operation to read a first page corresponding to a first word line of the flash memory according to a read command of a host, and perform a distribution-adjustment procedure when data read by the first read operation cannot be recovered by coding, wherein the controller is further configured to perform an adjustable read operation to read a second page corresponding to a second word line of the flash memory in the distribution-adjustment procedure.