Temperature-Adaptive Auto Refresh Limiting for DRAM Power Reduction
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Solution Overview
Problem
Semiconductor memory devices, such as DRAM, face data loss due to leakage current, which increases with internal temperature, leading to high power consumption during refresh operations, particularly in portable devices where power management is critical.
Innovation Solution
An auto refresh limiting circuit that generates an internal oscillating signal reflecting the device's temperature, using a masking signal to adjust the number of auto refresh pulses, thereby reducing unnecessary refresh operations and minimizing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auto refresh operation is performed frequently to prevent data loss from leakage current, then data integrity is maintained, but power consumption increases significantly
Solution Approach 1:
The patent implements dynamic adjustment of auto refresh execution based on temperature conditions. The refresh controller selectively enables or disables auto refresh operations according to real-time temperature measurements, making the refresh frequency adaptive rather than fixed. This resolves the contradiction by maintaining data integrity when needed (high temperature) while reducing power consumption when not needed (low temperature).
Solution Approach 2:
The patent changes the operational parameters of the refresh system by introducing temperature as a control variable. By measuring temperature and using it to modulate the auto refresh command signal, the system dynamically adjusts the refresh rate parameter. This allows the system to optimize between data integrity and power consumption by varying the refresh frequency according to actual leakage risk conditions.
2Reliability
If auto refresh command signal is continuously generated to ensure frequent refresh operations, then data loss is prevented, but the number of unnecessary refresh operations increases
Solution Approach 1:
The patent extracts the temperature-dependent control function from the continuous auto refresh command signal. By introducing a separate temperature sensing and evaluation path, the system can selectively gate the auto refresh commands based on actual need. This separates the continuous command generation from the actual execution, allowing unnecessary refresh operations to be eliminated while maintaining data integrity when required.
Solution Approach 2:
The patent implements a feedback mechanism where temperature measurements are continuously monitored and fed back to the refresh controller. This feedback loop allows the system to adjust auto refresh execution in real-time based on actual leakage conditions, preventing unnecessary refresh operations while ensuring data integrity when temperature indicates high leakage risk.
3Reliability
If refresh operation frequency is increased to compensate for temperature-dependent leakage current, then data retention is improved, but power consumption increases
Solution Approach 1:
The patent makes the refresh operation frequency dynamic by coupling it with temperature measurements. Instead of using a fixed high frequency to compensate for worst-case leakage, the system adjusts refresh frequency in real-time based on actual temperature conditions. This dynamic approach maintains data retention when temperature rises (increasing leakage) while reducing power consumption when temperature is low.
Solution Approach 2:
The patent changes the refresh frequency parameter based on temperature conditions. By using temperature as a control parameter to modulate refresh frequency, the system optimizes the balance between data retention and power consumption. The refresh rate is increased only when temperature indicates elevated leakage risk, and reduced when temperature is low, eliminating unnecessary energy consumption.
Data Source
AI summary
An auto refresh limiting circuit includes an oscillating signal generating part that generates an internal oscillating signal, the internal oscillating signal being a pulse having a period reflecting an internal temperature of a semiconductor memory device; a masking signal generating part that generates a masking signal by using an auto refresh command signal and the internal oscillating signal, the masking signal being deactivated during a pulse of the auto refresh command signal, the pulse of the auto refresh command signal being first generated after the pulse of the internal oscillating signal is generated; and an auto refresh masking part that converts the pulse of the auto refresh command signal into a pulse of an auto refresh driving signal, the conversion of the pulse of the auto refresh driving signal being masked according to the activation of the masking signal.