Memory System Read Voltage Order Adaptation
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Solution Overview
Problem
The existing memory systems face challenges in maintaining read operation efficiency due to temporary changes in threshold voltage distributions caused by program or erase operations, leading to increased read errors and the need for retry steps.
Innovation Solution
A memory system that determines the order of applying read voltages based on a preset table, performing read operations sequentially with optimized voltage application orders to prevent read failures and minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a program operation or erase operation is performed on a first memory block, then the memory operation is completed, but the threshold voltage distribution for neighboring memory blocks temporarily changes causing read errors
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple read voltage application orders in a table before actual read operations occur. When a program or erase operation is detected on a first memory block, the system proactively selects an appropriate read voltage application order from the pre-prepared table for subsequent read operations on affected memory blocks, rather than using a fixed default order. This preliminary preparation of multiple voltage application sequences enables the system to adapt to threshold voltage distribution changes and prevents read errors.
2Ease of operation
If a fixed read voltage application order is used, then the read operation process is simple, but read operations fail when threshold voltage distribution changes occur
Solution Approach 1:
The patent implements dynamics by making the read voltage application order changeable based on operational conditions. Instead of using a single fixed read voltage application order, the system maintains multiple read voltage application orders in a table and dynamically selects the appropriate order based on whether a program or erase operation has recently occurred on neighboring memory blocks. This dynamic adaptation allows the read operation process to remain simple in normal conditions while automatically adjusting to prevent read errors when threshold voltage distributions change.
3Reliability
If multiple read voltage application orders are maintained in a table, then read operation reliability improves, but device complexity increases
Solution Approach 1:
The patent reduces control logic complexity through preliminary action by pre-defining multiple read voltage application orders in a table during the design phase. The controller is configured to store this table containing multiple read voltage application orders, each corresponding to different operational scenarios. When a program or erase operation is detected, the controller simply looks up and selects the appropriate pre-defined order from the table based on the detected condition, rather than computing or determining the voltage application order in real-time. This preliminary preparation significantly simplifies the runtime control logic while maintaining high read operation reliability.
Data Source
AI summary
A memory system includes a memory device including a plane including a plurality of memory blocks for storing multi-bit data; and a controller configured to detect, when a problem-causing operation is performed on a first memory block among the memory blocks, remaining memory blocks, except the first memory block, in the plane as being in a problem occurrence candidate group, search for a table, when a read command for a second memory block of the problem occurrence candidate group is received, for a read voltage application order corresponding to the second memory block, and control the memory device to perform a read operation on the second memory block by sequentially applying a plurality of read voltages according to the searched read voltage application order, wherein the problem-causing operation is a program operation or an erase operation.