Memory Controller Bit Correction via Multiple Read Voltages

Solution Overview

Problem

Current error correction codes (ECC) in memory storage devices are limited in their ability to correct errors beyond their correction capacity, leading to uncorrectable data errors.

Innovation Solution

The system employs multiple read voltages to identify and correct errors by comparing bit values obtained at different voltages, using a bit value corrector to generate corrected data and iteratively apply ECC procedures until successful correction is achieved.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional ECC procedures are used to correct errors in stored data, then data integrity is maintained within the correction capacity of the ECC, but errors exceeding the correction capacity cannot be fixed

Engineering Contradiction:

Improvedata integrityVSAvoiderror correction capacity

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system performs preliminary reads of the storage elements at multiple different read voltages before the ECC correction process. By obtaining multiple candidate data sets in advance at different voltage levels, the system creates a pool of potential correct values that can be used to correct errors exceeding the original ECC capacity, allowing the ECC to successfully correct more errors than its standard capacity would allow

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the read voltage parameter to obtain different data representations of the same storage elements. By varying the read voltage across multiple levels and comparing the resulting bit patterns, the system identifies bits that flip between different voltage readings as likely erroneous bits, enabling correction beyond the original ECC capacity

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If multiple read voltages are used to correct errors, then the ability to correct errors exceeds the original ECC capacity, but the complexity of the read and correction process increases

Engineering Contradiction:

Improveerror correction capacityVSAvoidcorrection process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system performs preliminary reads of the storage elements at multiple different read voltages before the ECC correction process. By obtaining multiple candidate data sets in advance at different voltage levels, the system creates a pool of potential correct values that can be used to correct errors exceeding the original ECC capacity, allowing the ECC to successfully correct more errors than its standard capacity would allow

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from comparing bit patterns obtained at different read voltages to identify erroneous bits. By analyzing which bits flip between different voltage readings, the system generates a feedback signal that indicates which bits are likely incorrect, guiding the ECC correction process to focus on these specific bits and reducing overall correction complexity

Inventive Principle:

Principle #23Feedback

3Measurement precision

If multiple read voltages are applied to storage elements, then bit errors can be identified through comparison, but additional read operations and processing time are required

Engineering Contradiction:

Improvebit value accuracyVSAvoidread operation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary reads of the storage elements at multiple different read voltages before the ECC correction process. By obtaining multiple candidate data sets in advance at different voltage levels, the system creates a pool of potential correct values that can be used to correct errors exceeding the original ECC capacity, allowing the ECC to successfully correct more errors than its standard capacity would allow

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies different read voltages selectively to identify bits with uncertain or erroneous values. Rather than uniformly processing all bits, the method focuses the additional read operations and comparison logic specifically on bits that flip between different voltage readings, optimizing the balance between measurement precision and time consumption

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9329934B2Data storage device and method to correct bit values using multiple read voltages

Publication Date: 2016.05.03 SANDISK TECHNOLOGIES LLC

AI summary

A data storage device includes a memory including a group of storage elements. The memory is configured to read the group of the storage elements. A controller is coupled to the memory. The controller is configured to, in response to a first error correction code (ECC) procedure determining that a first plurality of bit values obtained using a first read voltage to read the group of storage elements is uncorrectable, instruct the memory to read the group of the storage elements using a second read voltage to obtain a second plurality of bit values. The controller is further configured to compare the first plurality of bit values with the second plurality of bit values to identify a first set of bits having different values in the first plurality of bit values as compared to the second plurality of bit values and to change one or more values of the first plurality of bit values for one or more bits in the first set of bits to generate a first plurality of corrected bit values.