Memory System Error Rate Reduction via Dynamic Pre-Read Voltage
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Solution Overview
Problem
Existing memory systems face reliability issues due to increased error bits in most significant bit (MSB) data, which affect data storage and retrieval accuracy, especially after repeated program and erase operations.
Innovation Solution
A memory system and method that defines a management area based on the number of error bits in MSB data, using a lower pre-read voltage for data retrieval and programming within this area to reduce error rates and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a higher pre-read voltage is used for reading LSB data, then read accuracy is improved, but error bits increase in MSB data after repeated program and erase operations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pre-read voltage level based on the operational state of the memory. Specifically, when the number of program and erase operations exceeds a threshold, the system switches from using a first pre-read voltage (for normal operations) to a second, lower pre-read voltage (for management area operations). This voltage parameter adjustment resolves the contradiction by preventing excessive error bit generation in MSB data while maintaining acceptable read accuracy through the modified reading condition.
2Productivity
If repeated program and erase operations are performed, then data storage capacity is improved, but error bits in MSB data increase
Solution Approach 1:
The patent segments the memory into different operational areas: normal storage areas and management areas. The management area is specifically identified where the number of program and erase operations exceeds a threshold. By segmenting the memory this way, the system can apply different reading strategies to different segments - using the lower second pre-read voltage specifically for management area operations to prevent error propagation, while maintaining normal operations in other areas.
Solution Approach 2:
The system implements feedback by monitoring the number of program and erase operations and using this information to determine whether to switch to the second pre-read voltage. The memory controller counts the number of operations and compares it against a threshold, then adjusts the reading voltage accordingly. This feedback mechanism allows the system to maintain reliability in high-operation-count areas while preserving productivity in areas with fewer operations.
3Quantity of substance
If the number of program and erase operations is increased, then memory utilization is improved, but reliability of stored data deteriorates
Solution Approach 1:
The patent applies local quality by treating different regions of the memory differently based on their operational history. The management area (where operations exceed the threshold) receives special treatment with the second pre-read voltage, while other areas continue to use the first pre-read voltage. This localized approach allows the system to maintain high memory utilization across the entire memory space while protecting data reliability specifically in areas that have undergone excessive program and erase cycles.
Data Source
AI summary
A memory system and a method of operating the same are provided. The method includes reading least significant bit (LSB) data of a first physical page based on a first pre-read voltage and performing a most significant bit (MSB) program based on the LSB data of the first physical page when the MSB program is performed on the first physical page, defining a management area by comparing the number of error bits included in MSB data of the first physical page with a first threshold value, preforming an LSB program on a second physical page of the management area, reading LSB data of the second physical page based on a second pre-read voltage, which is lower than the first pre-read voltage, and performing the MSB program on the second physical page based on the LSB data of the second physical page.