Flash Memory Data Randomization Circuit for Read Margin Improvement
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Solution Overview
Problem
Flash memory devices face challenges in efficiently randomizing and de-randomizing data across multiple segments, leading to variations in threshold voltages of memory cells due to word line coupling, which affects read margins and overall performance.
Innovation Solution
A method and circuit configuration that generates a random sequence based on a seed assigned to each page, iteratively applying it to segments for randomization and de-randomization, using a pseudo-random sequence generator and mixer to combine data, thereby reducing threshold voltage variations and enhancing read margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is stored in flash memory devices, then data retention is achieved, but threshold voltage variations occur due to word line coupling
Solution Approach 1:
The patent applies preliminary randomization to data before it is programmed into the flash memory device. This preliminary action modifies the data distribution pattern to account for and compensate for the threshold voltage variations that will occur during storage, thereby maintaining read margins despite the coupling effects
Solution Approach 2:
The patent changes the parameter of data distribution by applying randomization algorithms that modify the statistical properties of stored data. This parameter change ensures that data patterns do not exacerbate threshold voltage variations, thereby improving reliability while maintaining manufacturing constraints
2Reliability
If randomization is applied to data, then read margins are improved, but device complexity increases
Solution Approach 1:
The patent segments the randomization process into distinct stages: pseudo-random sequence generation, data mixing, and de-randomization. This segmentation allows each function to be implemented with dedicated, simplified circuitry rather than a single complex randomization unit, thereby improving read margins while managing device complexity
Solution Approach 2:
The patent introduces a pseudo-random sequence generator as an intermediary component that produces sequences used to mix with data. This intermediary approach allows for controlled and reversible randomization, improving read margins while maintaining manageable circuit complexity through the use of standard pseudo-random generation techniques
3Manufacturing precision
If iterative randomization is applied to multiple segments, then data uniformity is improved, but processing time increases
Solution Approach 1:
The patent implements continuous randomization processing that operates iteratively across multiple segments without interruption. The pseudo-random sequence generator continuously produces sequences that are applied to each segment, maintaining data uniformity across all segments while minimizing idle time and optimizing processing throughput
Solution Approach 2:
The patent applies periodic randomization where pseudo-random sequences are systematically applied to different segments in a repeating pattern. This periodic approach ensures uniform data distribution across all segments while organizing processing in efficient cycles, thereby improving data uniformity without excessive time penalty
Data Source
AI summary
Random sequence data is sequentially generated based on a seed assigned to a selected memory space, and one of access-requested segments of the selected memory space is logically combined with the sequentially generated random sequence data to transfer the access-requested segment. The sequentially generating and the logically combining are iteratively performed until remaining access-requested segments all transferred.