QLC NAND Gray Code Mapping for Faster Program and Read

Solution Overview

Problem

NAND Flash memory devices face inefficiencies in program and read operations, particularly in Quad-Level Cell (QLC) memory devices, where the 8-16 scheme is faster for programming but has a smaller read margin and longer read time, while the 16-16 scheme is slower for programming but has a shorter read time, necessitating a method to combine faster program and read operations.

Innovation Solution

A method that translates user data into a first gray-coded programming value using a read gray code, which is then converted to a second gray-coded programming value based on a mapping relationship between read and program gray codes, allowing for faster program and read operations by utilizing the 16-16 scheme for reading and the 8-16 scheme for programming, optimizing the total read time in QLC NAND Flash memory cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the 8-16 scheme is used for programming, then programming speed is improved, but read time increases and read margin decreases

Engineering Contradiction:

Improveprogramming speedVSAvoidread time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent segments the gray code representation into two distinct schemes: an 8-16 gray code optimized for programming operations and a 16-16 gray code optimized for read operations. The peripheral circuit converts between these schemes, allowing each operation type to use the most efficient encoding, thereby resolving the contradiction between programming speed and read time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of gray code representation from a single scheme to multiple schemes (8-16 and 16-16). By dynamically selecting and converting between different gray code parameters based on the operation type (program vs. read), the system optimizes both programming speed and read time independently.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the 8-16 scheme is used for programming, then programming speed is improved, but read margin decreases

Engineering Contradiction:

Improveprogramming speedVSAvoidread margin

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent segments the gray code representation into two distinct schemes: an 8-16 gray code optimized for programming operations and a 16-16 gray code optimized for read operations. The peripheral circuit converts between these schemes, allowing each operation type to use the most efficient encoding, thereby resolving the contradiction between programming speed and read time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of gray code representation from a single scheme to multiple schemes (8-16 and 16-16). By dynamically selecting and converting between different gray code parameters based on the operation type (program vs. read), the system optimizes both programming speed and read time independently.

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If the 16-16 scheme is used for reading, then read time is reduced, but programming speed decreases

Engineering Contradiction:

Improveread timeVSAvoidprogramming speed

Core Design Contradiction:

Loss of timeVSSpeed

Solution Approach 1:

The patent segments the gray code representation into two distinct schemes: an 8-16 gray code optimized for programming operations and a 16-16 gray code optimized for read operations. The peripheral circuit converts between these schemes, allowing each operation type to use the most efficient encoding, thereby resolving the contradiction between programming speed and read time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameter of gray code representation from a single scheme to multiple schemes (8-16 and 16-16). By dynamically selecting and converting between different gray code parameters based on the operation type (program vs. read), the system optimizes both programming speed and read time independently.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11854613B2Program and read operations using different gray codes and memory device for performing the same

Publication Date: 2023.12.26 YANGTZE MEMORY TECH CO LTD

AI summary

A memory device is provided. The memory device includes an array of memory cells arranged in a plurality of rows, a plurality of word lines respectively coupled to the plurality of rows of the memory cells, and a peripheral circuit coupled to the word lines. The peripheral circuit is configured to convert a first value to a second value based on a mapping relationship between a read gray code and a program gray code, perform a program operation to program the second value into a memory cell as a state based on the read gray code, and perform a read operation to read out the state from the memory cell based on the read gray code to be the first value.