MLC Memory Partial-Page Compression for Faster Read Latency
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Solution Overview
Problem
NAND flash memory systems experience increased read latency due to the need for multiple reference voltage comparisons when switching from single level cell to multilevel cell architectures, leading to inefficiencies in data retrieval.
Innovation Solution
Implementing a read with partial page compression method that compresses data using Huffman encoding, allowing for parallel processing of sensing operations and reducing the amount of data output, thereby accelerating the read operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple reference voltage comparisons are performed in MLC memory systems, then data storage capacity is improved, but read latency increases
Solution Approach 1:
The patent applies preliminary action by performing compression encoding on the first partial page data before it is fully sensed, and simultaneously sensing the second partial page data. This overlapping of operations reduces the total read latency while maintaining the capacity benefits of MLC architecture.
Solution Approach 2:
The patent ensures continuity of useful action by continuously sensing memory cell data across multiple reference voltages while simultaneously compressing previously sensed data. The compression operation continues without interruption during the sensing of subsequent partial pages, maximizing resource utilization and reducing idle time.
2Loss of information
If full page data is sensed and output, then data completeness is improved, but output time and latency increase
Solution Approach 1:
The patent segments the full page data into multiple partial pages, each corresponding to different reference voltage comparisons. By sensing and compressing these partial pages separately and in parallel where possible, the system reduces the time required to output complete data while maintaining data completeness through recombination at the controller.
Solution Approach 2:
The patent applies partial action by compressing only the first partial page data immediately after sensing, while the second partial page is sensed in parallel. This selective compression of portions of the data reduces overall output time while the controller reconstructs the complete page from both partial pages.
3Productivity
If compression encoding is performed on all data, then data transmission efficiency is improved, but processing complexity increases
Solution Approach 1:
The patent applies partial action by performing compression encoding only on the first partial page data, while the second partial page data is sensed in parallel without immediate compression. This selective approach improves transmission efficiency for the compressed portion while avoiding the complexity of compressing all data simultaneously, with the controller handling the recombination.
Data Source
AI summary
A memory system includes a memory device, the memory device including a memory cell array and a compression encoder, the memory cell array including a first plurality of multi level cells (MLCs). The memory device is configured to generate a first partial page by performing one or more first sensing operations on the first plurality of MLCs using one or more first reference voltages, output the first partial page, generate a second partial page by performing a second sensing operation on the first plurality of MLCs based on a second reference voltage, the second reference voltage having a different voltage level than the one or more first reference voltages, generate a compressed second partial page by compressing the second partial page using the compression encoder, and output the compressed second partial page.