Memory Controller Temperature Coefficient Adjustment for Read Voltage
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Solution Overview
Problem
In multi-value nonvolatile semiconductor memory systems, the threshold distribution detected during distribution read does not accurately reflect the actual distribution due to the use of a single common temperature coefficient for read voltage adjustments, leading to discrepancies and errors in determining the threshold voltages of memory cells.
Innovation Solution
A memory system comprising a memory controller and a nonvolatile semiconductor memory that generates and adjusts read voltages based on specific temperature coefficients, allowing for accurate determination of threshold voltages by using different temperature coefficients for different read operations, ensuring alignment between distribution read and normal read threshold distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single common temperature coefficient is used for adjusting read voltages in distribution read, then the adjustment process is simplified, but the detected threshold distribution does not accurately reflect the actual distribution
Solution Approach 1:
The patent segments the temperature coefficient adjustment by creating separate temperature coefficient tables for different read voltage levels. Each table contains temperature coefficients specific to its voltage range, allowing differentiated adjustment for distribution read and normal read operations, thereby improving measurement precision without excessive complexity
Solution Approach 2:
The patent applies local quality by using different temperature coefficients for different read voltage levels and different read operations. The control section selects appropriate temperature coefficients from different tables based on the specific read operation being performed, ensuring that each local operation (distribution read or normal read) receives the most appropriate temperature compensation
2Measurement precision
If different temperature coefficients are used for different read voltages in distribution read, then the threshold distribution detection accuracy is improved, but the control complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing temperature coefficients in separate tables before actual read operations. The temperature coefficient tables are prepared in advance with coefficients corresponding to different read voltage levels, eliminating the need for complex real-time calculations during distribution read operations
Solution Approach 2:
The patent introduces an intermediary mechanism - the temperature coefficient tables and control section logic - that mediates between the read voltage selection and the actual threshold detection. This intermediary layer simplifies the control complexity by automating the selection process based on read command type and voltage level
Data Source
AI summary
According to one embodiment, a memory system includes a nonvolatile semiconductor memory and a memory controller. The memory controller has a first signal generation section that generates a first signal related with a read voltage used for read operation of the nonvolatile semiconductor memory, a second signal generation section that generates a second signal that specifies the temperature coefficient used for the correction for temperature of the read voltage, and a first interface section that outputs the first signal, the second signal and a read command. The nonvolatile semiconductor memory has a word line, a memory cell array includes memory cells connected to the word line, and a second interface section that receives the first signal, the second signal and the read command.