Dynamic Overcharge Voltage for Memory Refresh Cycle Extension
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Solution Overview
Problem
Current memory technologies face challenges in scaling threshold voltage with decreasing feature sizes, leading to shorter refresh cycle times and increased power usage due to more frequent refresh operations, which negatively impact memory access performance.
Innovation Solution
A refresh voltage control engine dynamically applies a higher overcharge voltage during refresh operations to extend the refresh cycle time, allowing for selective adjustment of refresh times based on the state and condition of memory device portions, thereby reducing the frequency of refreshes and conserving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If memory devices use smaller feature sizes and lower supply voltages, then manufacturing scalability is improved, but refresh cycle time decreases and power usage increases
Solution Approach 1:
The patent changes the voltage parameter by applying an overcharge voltage (Vblh_overcharge) higher than the normal bitline high voltage during refresh operations. This parameter change extends the refresh cycle time by storing more charge in the memory cell capacitors, thereby reducing the frequency of refresh operations and lowering overall power consumption despite using smaller feature sizes
Solution Approach 2:
The patent applies excessive action by charging the memory cell capacitors beyond the normal operating voltage level during refresh operations. This overcharging approach stores more than the minimum required charge, extending the time before the capacitor voltage drops below the threshold voltage, thus reducing refresh frequency and power usage
2Reliability
If refresh frequency is increased to maintain state in volatile memories, then data retention reliability is improved, but power consumption increases
Solution Approach 1:
The patent changes the voltage parameter by applying an overcharge voltage (Vblh_overcharge) higher than the normal bitline high voltage during refresh operations. This parameter change extends the refresh cycle time by storing more charge in the memory cell capacitors, thereby reducing the frequency of refresh operations and lowering overall power consumption while maintaining data retention reliability
3Reliability
If refresh frequency is increased to maintain state in volatile memories, then data retention reliability is improved, but memory access performance deteriorates
Solution Approach 1:
The patent changes the voltage parameter by applying an overcharge voltage (Vblh_overcharge) higher than the normal bitline high voltage during refresh operations. This parameter change extends the refresh cycle time by storing more charge in the memory cell capacitors, thereby reducing the frequency of refresh operations. This reduction in refresh frequency directly improves memory access performance by freeing up memory access resources while maintaining data retention reliability
Data Source
AI summary
A refresh voltage control engine selectively applies different high voltages to use in refresh operations. The control engine can detect that a portion of a memory device needs to be refreshed, and determine that the refresh cycle time is too short for a state of the portion of the memory device. The memory device typically has an associated refresh cycle time or time between refreshes based on the device and system architecture. The control engine can generate one or more control signals to cause the system to apply an overcharge refresh to overcharge the portion of the memory device with a refresh operation to extend the refresh cycle time for the portion of the memory device.