Internal Refresh Command Generation for Memory Power-Up Voltage Stability
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Solution Overview
Problem
Semiconductor memory devices like LPDDR2 RAM lack a mechanism to stabilize internal voltages during power-up, as they do not receive a refresh command, which is necessary for normal operations such as read or write operations.
Innovation Solution
An internal command generation device that generates an internal refresh command and performs a refresh operation within a device auto initialization period, setting up a reset period and device auto initialization period through flag signal generation and pulse signal management to stabilize the internal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the device enters power-up mode without external refresh commands, then the device can operate autonomously during initialization, but the internal voltage cannot be stabilized
Solution Approach 1:
The device performs self-initialization by autonomously generating internal refresh commands during the device auto initialization period without requiring external controller intervention. The internal command generation unit automatically creates refresh commands to stabilize internal voltages, enabling the device to service itself during power-up.
Solution Approach 2:
The system performs preliminary voltage stabilization actions during the device auto initialization period before normal operations begin. By generating internal refresh commands in advance during initialization, the system ensures voltages are stabilized before read/write operations start, preventing potential errors during subsequent operations.
2Reliability
If the device waits for external refresh commands during initialization, then voltage stabilization can be achieved, but the device cannot perform autonomous initialization
Solution Approach 1:
The device performs self-initialization by autonomously generating internal refresh commands during the device auto initialization period without requiring external controller intervention. The internal command generation unit automatically creates refresh commands to stabilize internal voltages, enabling the device to service itself during power-up.
3Reliability
If refresh operations are performed during device auto initialization, then internal voltage is stabilized, but the initialization period is extended
Solution Approach 1:
The system uses periodic refresh operations during the device auto initialization period to stabilize internal voltages. By implementing refresh commands at appropriate intervals within the initialization window, the system achieves voltage stabilization without excessively extending the initialization duration, balancing reliability and time efficiency.
Data Source
AI summary
The initial command generation device includes a first flag signal generation unit configured to generate a reset flag signal setting a reset period in response to a reset command, an initial pulse signal generation unit configured to generate a first initial pulse signal and a second initial pulse signal in response to the reset flag signal, a second flag signal generation unit configured to generate a device auto initialization flag signal setting a device auto initialization period in response to the first initial pulse signal and an internal command generation unit configured to generate an internal refresh command enabled within the device auto initialization period in response to the second initial pulse signal.