Flash Memory LSB Buffering for Reference Voltage Accuracy

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Flash memory controllers face challenges in accurately determining and programming reference voltage ranges due to physical non-uniformity and errors in LSB page data, leading to mis-programming and degraded error correction performance, especially as flash memory technology advances and cell sizes scale down.

Innovation Solution

The solution involves buffering copies of LSB page data to ensure error-free reference voltage determination, where the SSD controller maintains a temporary copy of the LSB page data written to flash cells, allowing it to accurately determine and program proper reference voltage ranges for MSB page programming, thereby preventing mis-programming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the flash memory controller reads LSB page data directly from flash cells to determine reference voltage ranges, then the process is simple and fast, but programming errors occur due to physical non-uniformity and detection inaccuracies

Engineering Contradiction:

Improveprogramming speedVSAvoidprogramming accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by buffering the LSB page data after successful programming before using it to determine reference voltage ranges. This ensures that the data used for voltage determination is error-free, preventing mis-programming of reference voltages while maintaining efficient processing flow.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If error-correcting codes are used to improve bit error rate, then reliability improves, but the effectiveness diminishes as cell features scale down due to increased physical non-uniformity

Engineering Contradiction:

Improvebit error rateVSAvoidcell feature uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses a copy of the buffered LSB page data to determine reference voltage ranges. This copying approach ensures that the data used for voltage determination is a reliable replica of the successfully programmed data, eliminating the need for complex error correction while maintaining high reliability even as cell features scale down.

Inventive Principle:

Principle #26Copying

3Measurement precision

If multiple reference voltages are provided for MLC/TLC flash memory, then detection accuracy improves, but the complexity of the controller increases

Engineering Contradiction:

Improvedata detection accuracyVSAvoidcontroller complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback by using the buffered LSB page data to determine reference voltage ranges for MSB programming. This feedback mechanism ensures that the reference voltages are dynamically adjusted based on actual programming results, improving detection accuracy without requiring complex fixed reference voltage structures.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9477423B2Eliminating or reducing programming errors when programming flash memory cells

Publication Date: 2016.10.25 SEAGATE TECH LLC

AI summary

Mis-programming of MSB data in flash memory is avoided by maintaining a copy of LSB page data that has been written to flash memory and using the copy rather than the LSB page data read out of the flash cells in conjunction with the MSB values to determine the proper reference voltage ranges to be programmed into the corresponding flash cells. Because the copy is free of errors, using the copy in conjunction with the MSB values to determine the proper reference voltage ranges for the flash cells ensures that mis-programming of the reference voltage ranges will not occur.