Temperature-Controlled Column Selection for Nonvolatile Memory
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Solution Overview
Problem
Nonvolatile memory devices, particularly phase-change random access memory (PRAM) devices, face challenges in maintaining accurate data writing and reading performance across varying temperatures due to changes in electric resistance along the path of write/read currents, leading to potential errors.
Innovation Solution
A nonvolatile memory device with a hierarchical bitline structure and a temperature-regulated column selection circuit that adjusts the level of column selection signals and column bias in response to temperature changes, ensuring a consistent penetration current through memory cells, thereby compensating for temperature-induced variations in resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the column selection signal level is kept constant, then the device complexity is reduced, but the write/read performance deteriorates at varying temperatures due to resistance changes
Solution Approach 1:
The column selection signal level is made dynamic rather than fixed. The controller adjusts the signal level based on temperature conditions to maintain consistent penetration current through the memory cells, resolving the contradiction between constant simplicity and variable performance
Solution Approach 2:
The voltage level of the column selection signal is changed as a parameter in response to temperature variations. By modifying this electrical parameter, the system compensates for resistance changes in the memory cell path, maintaining reliable write/read operations across different temperatures
2Reliability
If temperature compensation is implemented, then the reliability improves across temperature ranges, but the device complexity increases due to additional control circuits
Solution Approach 1:
A feedback mechanism is implemented where the controller monitors temperature conditions and adjusts the column selection signal level accordingly. This feedback loop enables automatic compensation for temperature-induced resistance changes, improving reliability while keeping the control integrated within existing circuitry
Solution Approach 2:
The controller is designed to perform multiple functions: normal memory control operations and temperature-based signal level adjustment. By making the controller multi-functional, the patent avoids adding separate dedicated temperature compensation circuits, thus improving reliability without proportionally increasing device complexity
Data Source
AI summary
A nonvolatile memory device includes a memory cell array with a matrix of nonvolatile memory cells. The nonvolatile memory cells may store data using variable resistive elements. A plurality of bitlines are coupled to a plurality of nonvolatile memory cell arrays in the memory cell array. A column selection circuit selects among the bitlines in response to a column selection signal. A controller regulates a level of the column selection signal in response to a temperature signal from a temperature sensor. The temperature sensor may be configured to measure temperature outside the nonvolatile memory device to generate the temperature signal.