Memory Controller Data Compression and Padding for Wear Balancing

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Solution Overview

Problem

Flash memory durability degrades as the amount of electric charge injected into memory cells increases, leading to wear and reduced performance, especially in multi-level cell modes where the distribution with the maximum threshold voltage experiences the highest wear, limiting independent read and write operations on upper and lower pages.

Innovation Solution

A memory controller with a compression unit and padding processing unit that compresses data and adds padding data to minimize the number of cells with maximum threshold voltage distributions, distributing compression and padding data across upper and lower pages to balance wear and enable independent page operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If data is written to flash memory cells, then storage capacity is utilized, but durability degrades due to increased electric charge injection

Engineering Contradiction:

Improvestorage capacity utilizationVSAvoidmemory durability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by distributing data writing to different threshold voltage distributions across multiple pages. Instead of concentrating writes in a single distribution, the system divides data across pages with different threshold voltage characteristics, thereby localizing wear to specific regions and preserving overall memory durability while maintaining storage capacity utilization.

Inventive Principle:

Principle #3Local quality

2Productivity

If compression is applied to data pages, then storage efficiency improves, but the distribution of threshold voltages becomes unbalanced causing wear concentration

Engineering Contradiction:

Improvestorage efficiencyVSAvoidwear distribution balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments compressed data across multiple pages with different threshold voltage distributions. By dividing the compressed data stream and distributing it to different pages (e.g., upper page, lower page, extra page), the system maintains storage efficiency through compression while preventing wear concentration by spreading the electrical stress across multiple threshold voltage distributions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of data distribution by allocating compressed data to pages with different threshold voltage characteristics. This parameter change ensures that no single threshold voltage distribution bears excessive wear, thereby maintaining reliability while preserving the storage efficiency benefits of compression.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If padding data is added to balance wear distribution, then durability improves, but the number of cells with maximum threshold voltage increases

Engineering Contradiction:

Improvewear distribution balanceVSAvoidnumber of cells with maximum threshold voltage

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent inverts the conventional approach by not adding padding data to fill spaces, but rather strategically distributing compressed data to pages where it naturally balances wear. Instead of using padding to achieve balance (which increases maximum threshold voltage cells), the system redistributes actual data across pages to achieve wear balance without increasing the number of maximum threshold voltage cells.

Inventive Principle:

Principle #13The other way round (Inversion)

4Ease of operation

If independent read and write operations are enabled on upper and lower pages, then operational flexibility improves, but wear concentration on maximum threshold voltage distribution occurs

Engineering Contradiction:

Improveoperational flexibilityVSAvoidwear concentration

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent enables universal wear balancing across multiple page types (upper page, lower page, extra page) that can independently handle read and write operations. Each page type serves multiple functions: storing data, balancing wear, and supporting independent operations. This multi-functionality allows operational flexibility while preventing wear concentration through distributed writing across all page types.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9971523B2Memory controller with data compression and padding features, method of controlling nonvolatile memory and memory system

Publication Date: 2018.05.15 KIOXIA CORP

AI summary

According to one embodiment, a memory controller includes a compression unit and a padding processing unit. The compression unit compresses first data to be written into a first page and second data to be written into a second page. The padding processing unit performs a padding processing such that the compressed first data is written into first memory cells, first padding data is written into second memory cells, the compressed second data is written into third memory cells, and second padding data is written into fourth memory cells.