Nonvolatile Memory Read Voltage Calibration Across Temperature
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Solution Overview
Problem
The threshold voltage of memory cell transistors in conventional memory systems can change due to various factors, leading to erroneous data determination during read operations, which existing systems address through shift reading by adjusting read voltages, but this method is inefficient and prone to errors.
Innovation Solution
A memory system incorporating a non-volatile first memory, a second memory storing temperature-dependent threshold voltage information, and a controller that adjusts read voltages based on temperature readings to minimize error bits, using shift and mask data readings to determine optimal read voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shift reading is executed to correct erroneous data determination, then data accuracy can be improved, but reading time and system complexity increase significantly
Solution Approach 1:
The system performs preliminary action by acquiring optimal read voltages in advance and storing them in a table structure organized by temperature ranges. During normal read operations, the controller simply retrieves the pre-calculated optimal voltage for the current temperature range, eliminating the need for time-consuming shift reading procedures while maintaining high data accuracy.
Solution Approach 2:
The system implements dynamics by making read voltages adaptive to temperature changes. The controller dynamically selects appropriate read voltages from the stored table based on detected temperature ranges, allowing the system to optimize reading accuracy for different thermal conditions without executing time-consuming shift reading operations each time.
2Measurement precision
If multiple shift reading operations are performed to find optimal read voltage, then data determination accuracy improves, but the number of operations and time consumption increase
Solution Approach 1:
The system performs the complex task of finding optimal read voltages through multiple shift reading operations in advance, during initialization or calibration phases. The results are stored in a lookup table that maps temperature ranges to optimal read voltages. During normal operations, the system simply queries this pre-computed table, achieving high measurement precision without repeating the time-consuming search process.
Solution Approach 2:
The system creates a copy of the optimal read voltage information in a stored table structure. Instead of performing multiple shift reading operations each time data needs to be read, the controller retrieves the copied optimal voltage values from the table based on current temperature conditions, significantly improving reading efficiency while maintaining determination accuracy.
3Productivity
If read voltage values are stored for each temperature range in a table, then optimal reading can be achieved quickly, but memory requirements and system complexity increase
Solution Approach 1:
The system manages complexity by organizing read voltage data according to temperature range parameters. The table stores optimal read voltages indexed by temperature ranges, allowing the controller to quickly retrieve appropriate voltages by simply determining the current temperature range. This parameter-based organization enables fast voltage adjustment while keeping the data structure manageable and the control logic relatively simple.
4Reliability
If conventional shift reading is used to handle threshold voltage changes, then erroneous determination can be corrected, but the process becomes inefficient and error-prone
Solution Approach 1:
The system implements feedback by using temperature detection to automatically select appropriate read voltages from the stored table. The temperature sensor provides continuous feedback about thermal conditions, and the controller uses this information to retrieve the optimal read voltage for the current temperature range, ensuring reliable data determination without manual intervention or complex shift reading procedures.
Data Source
AI summary
According to an embodiment, a controller acquires a first temperature detection value and executes an acquisition operation on a first storage area. The controller converts a first voltage value into a second voltage value representing the read voltage in a temperature set value based on the first temperature detection value and records the second voltage value. The acquisition operation is an operation of determining, by using the read voltages, whether memory cells are ON or OFF and acquiring the first voltage value representing the read voltage for suppressing error bits. After that, the controller acquires a second temperature detection value and converts the second voltage value into a third voltage value representing the read voltage in the second temperature detection value. The controller reads data from the memory cells by using, as the read voltage, a voltage indicated by the third voltage value.