Multi-Die Read Reference Voltage Selection for NAND Accuracy
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Solution Overview
Problem
As integration density increases in non-volatile memory systems like NAND flash, read operation errors rise due to changes in threshold voltage distributions caused by varying operating environments, necessitating accurate adjustment of the reference voltage for multi-dies to ensure data integrity.
Innovation Solution
A method to determine a common optimal read reference voltage for multi-dies by analyzing voltage distributions at different temperatures and P/E cycles, identifying optimal voltages with the lowest error rates, and selecting the most frequently occurring voltage as the common optimal read reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If integration density of flash memory is increased, then operation speed is improved, but read operation errors increase due to threshold voltage distribution changes
Solution Approach 1:
The patent applies parameter changes by adjusting the read reference voltage based on temperature conditions and P/E cycle counts. The memory controller dynamically selects optimal read reference voltages from multiple candidates depending on the current operating temperature and the number of program/erase cycles the memory has undergone, thereby compensating for threshold voltage shifts caused by high integration density and environmental variations.
2Measurement precision
If read reference voltage is adjusted for each block, then read accuracy is improved, but system complexity increases
Solution Approach 1:
The patent implements local quality by determining optimal read reference voltages for each block individually based on its specific voltage distribution characteristics, temperature conditions, and P/E cycle history. Each block can have its own optimized reference voltage selected from a set of candidate voltages, allowing localized optimization without requiring a completely separate adjustment system for each block.
Solution Approach 2:
The patent applies preliminary action by pre-determining optimal read reference voltages for each block during manufacturing or initialization based on their voltage distribution characteristics. These optimal voltages are stored and can be quickly retrieved and applied during read operations, avoiding the need for complex real-time calculations during actual data reading.
3Productivity
If common optimal read reference voltage is selected for multi-dies, then manufacturing efficiency is improved, but individual die performance may be compromised
Solution Approach 1:
The patent resolves this contradiction by maintaining multiple candidate read reference voltages and selecting the most appropriate one for each die based on its specific characteristics and operating conditions. While a common set of candidate voltages is used across multiple dies (improving manufacturing efficiency), the actual selected voltage for each die is optimized individually based on its voltage distribution, temperature, and P/E cycle count (maintaining individual die performance).
Data Source
AI summary
A method for finding a common optimal read reference voltage of multi-dies and a storage system includes: obtaining voltage distributions of each block in the multi-dies at different read and write temperatures and/or different P/E cycles; determining optimal read reference voltages for all blocks in the multi-dies; obtaining the number of blocks corresponding to different optimal read reference voltages according to the optimal read reference voltages of all blocks in the multi-dies; and selecting the optimal read reference voltage with the most occurrences as the common optimal read reference voltage according to the number of blocks corresponding to the different optimal read reference voltages.