Memory Controller Temperature Compensation for Read Accuracy
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Solution Overview
Problem
Conventional memory systems face challenges in accurately reading data due to variations in threshold voltage caused by temperature changes, leading to errors in data retrieval, especially when the temperature differs between program and read operations, which affects the determination voltage and results in increased error bits and reduced read performance.
Innovation Solution
A memory system that includes a nonvolatile memory, a temperature sensor, and a controller, which measures temperature differences and adjusts the determination voltage using a correction algorithm to minimize errors by setting the threshold voltage of memory cell transistors accordingly, allowing for accurate data retrieval even under varying temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed determination voltage is used for read operations, then the circuit design is simple, but read accuracy deteriorates when temperature varies between program and read operations
Solution Approach 1:
The determination voltage is made dynamic rather than fixed. The voltage changes based on the temperature difference between program and read operations. The control circuit adjusts the determination voltage in real-time according to temperature conditions, allowing the system to adapt to varying thermal environments and maintain read accuracy without requiring overly complex circuit design
Solution Approach 2:
The determination voltage parameter is changed based on temperature conditions. When the temperature difference between program and read operations exceeds a threshold, the system modifies the determination voltage value to compensate for threshold voltage shifts in memory cell transistors. This parameter adjustment resolves the contradiction by maintaining measurement precision through adaptive voltage selection
2Reliability
If the determination voltage is adjusted to compensate for temperature variations, then read accuracy improves, but the device complexity increases due to additional temperature sensing and voltage adjustment circuits
Solution Approach 1:
The control circuit is designed to perform multiple functions: it manages normal read operations, senses temperature differences (or receives temperature information), adjusts determination voltages when needed, and maintains compatibility with existing memory interfaces. By making the control circuit multi-functional rather than adding completely separate systems, the patent improves reliability while minimizing the increase in device complexity
Solution Approach 2:
A temperature information interface acts as an intermediary between the temperature sensor and the control circuit. This intermediary layer allows the system to obtain temperature data without requiring the control circuit to directly interface with complex temperature sensing mechanisms, thereby improving read performance while keeping the overall system structure manageable
3Reliability
If temperature compensation is implemented, then the number of error bits decreases, but the operation time increases due to temperature measurement and voltage correction steps
Solution Approach 1:
Temperature information is acquired or measured in advance before the read operation proceeds to data retrieval. By obtaining temperature data beforehand and pre-calculating the appropriate determination voltage, the system minimizes the time added to the read operation. The compensation is prepared in advance rather than being calculated in real-time during the critical data reading phase
Solution Approach 2:
The system applies temperature compensation selectively rather than unconditionally. Compensation is performed only when the temperature difference between program and read operations exceeds a predetermined threshold. This partial application of compensation reduces the number of error bits in cases that need it while avoiding unnecessary time overhead in cases where temperature conditions are stable
Data Source
AI summary
According to one embodiment, a memory system includes a first nonvolatile memory, and a controller. The controller executes, to the first memory, a program operation first and a first read operation next. The program operation is an operation including (i) acquiring a first temperature, (ii) storing the first temperature, and (iii) controlling the access circuit to set a threshold voltage of a memory cell transistor at a value corresponding to first data. The first read operation is an operation for (i) acquiring a second temperature, (ii) computing a difference between the second and the first temperature, (iii) acquiring a first determination voltage, (iv) correcting the first determination voltage according to the difference, and (v) controlling the first memory to acquire second data corresponding to the threshold voltage on the basis of a comparison between the threshold voltage of the memory cell transistor and the corrected first determination voltage.