NAND Read Retry Voltage Offsets for Open and Closed Blocks
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Solution Overview
Problem
Existing memory systems face challenges in accurately reading data from NAND memory due to variations in word line states and voltage offsets, leading to read errors and inefficiencies.
Innovation Solution
A memory system and method that utilizes a first-type and second-type read retry table to adjust read retry voltages based on the state of memory blocks and word line relationships, incorporating voltage offset values to enhance read accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single read retry table is used for all memory blocks, then the device complexity is reduced, but the read accuracy deteriorates due to variations in word line states
Solution Approach 1:
The patent divides the read retry table into two separate types: first-type read retry tables for closed memory blocks and second-type read retry tables for open memory blocks. Each type contains voltage offset values specific to its block state, allowing accurate compensation for threshold voltage shifts without requiring a single complex table to handle all scenarios.
Solution Approach 2:
The patent applies different voltage offset values from appropriate read retry tables based on the specific state of each memory block (open or closed) and the position of word lines. This localized approach ensures that each memory block receives the most suitable voltage compensation for its particular condition, maximizing read accuracy.
2Reliability
If voltage offset values are not adjusted for open blocks, then the operation speed is maintained, but the read reliability deteriorates due to threshold voltage shifts
Solution Approach 1:
The patent pre-calculates and stores voltage offset values in the second-type read retry tables for open memory blocks before read operations occur. When reading from an open block, the controller quickly retrieves the appropriate pre-computed offset values and applies them to compensate for threshold voltage shifts, avoiding the need for complex real-time calculations during the read operation itself.
3Measurement precision
If the read retry table is expanded to include all word line states, then the read accuracy is improved, but the memory space consumption increases
Solution Approach 1:
The patent segments the comprehensive read retry data into two separate first-type tables (for closed blocks) and second-type tables (for open blocks). This segmentation reduces the total memory space required compared to storing all possible word line states in a single table, while still providing accurate voltage compensation for each specific block state.
Solution Approach 2:
The first-type read retry tables serve as a foundation for both closed and open block scenarios, while the second-type tables provide additional adjustments specifically for open blocks. This multi-functional approach allows the system to handle different block states using a combination of tables rather than requiring completely separate tables for every possible state.
Data Source
AI summary
A memory system, an operation method thereof and a readable storage medium are provided according to examples of this disclosure. The memory system including: a memory device including a plurality of memory blocks, each of which including a plurality of word lines and a plurality of memory cells coupled to the plurality of word lines; a memory controller coupled to the memory device and configured to: acquire a read retry voltage with both a first-type read retry table and a second-type read retry table; control the memory device to perform a read retry operation with the read retry voltage.