DRAM Self-Refresh Control via Bulk Voltage Segmentation
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Solution Overview
Problem
Current self-refresh technologies in DRAMs face challenges in reducing current consumption during standby states, leading to limited battery life in mobile devices, as existing methods for terminating self-refresh operations are not efficient and can result in unstable bulk voltage levels, causing data loss and increased power consumption.
Innovation Solution
A self-refresh control device utilizing a bulk-bias control scheme that combines idle and self-refresh signals to generate a control signal for varying bulk voltage levels, stabilizing the self-refresh operation by maintaining consistent bulk voltage during active bank operations and reducing off-leakage currents through PMOS transistor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-refresh operation is performed in DRAM standby state, then data retention is maintained, but current consumption increases
Solution Approach 1:
The patent divides the bulk voltage control into different segments based on operation mode. During self-refresh, a first bulk voltage is applied to reduce leakage current, while during active operations, a second bulk voltage is applied to maintain performance. This segmentation allows optimized voltage control for different operational states, reducing overall power consumption while maintaining data retention.
Solution Approach 2:
The patent dynamically adjusts the bulk voltage level based on the operational state of the DRAM. The bulk voltage controller switches between different voltage levels depending on whether the device is in self-refresh mode or active mode, enabling adaptive power management that reduces current consumption during standby while maintaining reliability.
2Use of energy by moving object
If bulk voltage is varied to reduce off-leakage currents, then power consumption decreases, but bulk voltage stability deteriorates
Solution Approach 1:
The patent employs a bulk voltage controller that receives feedback signals (such as idle signals and self-refresh signals) to dynamically adjust the bulk voltage. This feedback mechanism ensures that the bulk voltage is varied only when appropriate (during self-refresh with idle banks), maintaining stability during active operations while enabling power reduction during standby states.
Solution Approach 2:
The bulk voltage controller acts as an intermediary between the operational state signals and the bulk voltage driver. It processes signals such as idle signals and self-refresh signals to determine the appropriate bulk voltage level, thereby mediating between power reduction goals and voltage stability requirements.
3Productivity
If self-refresh termination is achieved by CKE deactivation, then refresh operation stops, but operation timing becomes asynchronous
Solution Approach 1:
The patent enables the DRAM to autonomously manage its self-refresh termination through internal signal generation and detection. The system uses idle signals generated internally to determine when all banks are idle, allowing the device to self-regulate its refresh operations without requiring external CKE deactivation, thereby maintaining synchronization while achieving termination.
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
The solution effectively reduces self-refresh current consumption, stabilizes the self-refresh operation, and prevents data loss by maintaining consistent bulk voltage levels, thereby extending battery life in mobile devices.
Implementation Method 1
A self-refresh control device utilizing a bulk-bias control scheme that combines idle and self-refresh signals to generate a control signal for varying bulk voltage levels
Data Source
AI summary
Provided is a device and method for controlling self-refresh which reduces current when a semiconductor device stays in a self-refresh operation. The device for controlling self-refresh includes a bulk voltage controller configured to combine an idle signal indicating an active termination state of a bank and a self-refresh signal so as to generate a control signal for controlling a bulk voltage, a bulk voltage driver configured to vary a level of the bulk voltage in response to the control signal, and output the bulk voltage with a different level, and a refresh controller configured to output the self-refresh active signal upon receiving the bulk voltage as a bulk bias voltage.