Memory Read Voltage Control for Power-Off Temperature Shifts
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Solution Overview
Problem
Memory devices are prone to malfunctions when transitioning from a power-off to a power-on state due to unknown temperature changes during the off-state, affecting their operation and data integrity.
Innovation Solution
A memory device with an off-temperature determination circuit that generates an off-temperature code based on the threshold voltage of memory cells, allowing for controlled read voltage adjustments based on temperature changes, ensuring reliable operation even in power-off conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory device operates without temperature monitoring during power-off state, then the device complexity is reduced, but the reliability deteriorates due to unknown temperature changes causing malfunctions
Solution Approach 1:
The patent applies preliminary action by determining the temperature condition during the power-off state before the memory device is powered on. The off-temperature determination circuit measures the threshold voltage of memory cells while powered off to infer the temperature the device experienced during the off-state, enabling proactive adjustment of read voltages before actual operation begins, thus preventing potential malfunctions.
Solution Approach 2:
The patent uses threshold voltage as an intermediary parameter to indirectly measure temperature. Instead of directly measuring temperature during power-off state, the circuit measures the threshold voltage of memory cells, which changes with temperature, and uses this voltage measurement to determine the off-state temperature condition and adjust operational parameters accordingly.
2Adaptability or versatility
If the read voltage is adjusted based on off-temperature code, then the adaptability to temperature changes is improved, but the device complexity increases due to additional control circuits
Solution Approach 1:
The patent achieves multi-functionality by using the same memory cell array for both data storage and temperature sensing purposes. The memory cells serve dual roles: storing user data and acting as sensors to detect threshold voltage changes that indicate temperature conditions during power-off state, eliminating the need for separate dedicated temperature sensors.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the read voltage parameter based on the determined off-temperature condition. The control circuit selects different read voltage levels from a set of available voltages depending on the off-temperature code, allowing the memory device to adapt its operational parameters to compensate for temperature-induced threshold voltage shifts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures stable data storage and retrieval by adapting read voltage levels to temperature changes, maintaining operational reliability during power transitions.
Implementation Method 1
generating an off-temperature code based on a characteristic of at least one memory cell in a specific region of the memory cell array, the off-temperature code indicating a temperature change occurred in the memory device in a power off state
Data Source
AI summary
A memory device may include a memory cell array including a plurality of memory cells, an off-temperature determination circuit configured to generate an off-temperature code based on a level of a threshold voltage of at least one memory cell included in a specific region of the memory cell array, a control circuit configured to generate a voltage control signal based on the off-temperature code, and a read voltage generation circuit configured to provide a read voltage to the memory cell array based on the voltage control signal.