Volatile Memory Self-Refresh Control for Power-Off Data Retention
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Solution Overview
Problem
The high current consumption due to self-refresh operations in volatile memory devices, such as DRAM, when a vehicle's power is turned off, is a significant issue that increases energy waste and resource inefficiency.
Innovation Solution
Implementing a control logic in volatile memory devices to manage self-refresh operations, including a self-refresh timer and command timer, which triggers data transfer to non-volatile memory after a threshold time and powers off the volatile memory when data transfer is complete, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If volatile memory performs self-refresh operation to maintain data when ECU is powered off, then data retention is improved, but current consumption increases
Solution Approach 1:
The system performs preliminary data transfer from volatile memory to non-volatile memory before the ECU is completely powered off. The control logic monitors the power-off state and initiates data transfer when the power-off condition is detected, ensuring data is saved before power is fully cut. This allows the volatile memory to be powered off after data transfer, reducing continuous self-refresh operations and lowering current consumption while maintaining data retention reliability.
2Reliability
If volatile memory continues self-refresh operation after data transfer is complete, then data retention is maintained, but power consumption is wasted
Solution Approach 1:
The control logic continuously monitors the power state and transfer status to determine when self-refresh operations should continue and when they should stop. When data transfer to non-volatile memory is complete and the ECU is fully powered off, the control logic receives feedback that power consumption should be reduced by stopping self-refresh operations. This feedback mechanism ensures energy is not wasted on unnecessary self-refresh operations after data retention is no longer required.
3Reliability
If control logic monitors read commands continuously to determine power-off state, then accurate power state detection is improved, but operational complexity increases
Solution Approach 1:
The control logic uses the volatile memory device's own operational state and the ECU's power state to determine when data transfer should occur. The monitoring of read commands and detection of power-off conditions are performed by the control logic itself without requiring external intervention or complex additional monitoring circuits. This self-service approach simplifies the overall system while maintaining accurate power state detection and appropriate data transfer timing.
Data Source
AI summary
A volatile memory device comprises a memory cell array including a plurality of memory cells storing data, and control logic controlling read and write operations for the plurality of memory cells. The control logic is configured to receive a command instructing a self-refresh operation from an external host device, to perform the self-refresh operation in response to the received command, to request the external host device to transfer data stored in the plurality of memory cells in response to a performance time of the self-refresh operation having elapsed a first threshold time, to monitor a read command received from the external host device in response to receiving a notification of self-refresh operation termination and a read command from the external host device, and to enter a power off state in response to the read command not being received for a second threshold time.