Power Management Unit Controlled Shutdown Sequence
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Solution Overview
Problem
Unexpected reset or power-down events in computing devices can interrupt active functional blocks, leading to errors and reliability issues due to incomplete programming operations in non-volatile memory, data loss in volatile memory, and undesirable effects like 'ghosting' in displays and communication interruptions.
Innovation Solution
A system with a power management unit (PMU) that generates power supply voltages and changes status signals in response to events, allowing for controlled transitions between operating modes, canceling pending commands, and sending refresh commands to volatile memory, thereby ensuring complete active commands are finished before voltage reduction, and transitioning to inactive or reset states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the system transitions to power-down or reset state immediately when a power loss event is detected, then the response time is reduced, but active functional blocks are interrupted causing errors and reliability issues
Solution Approach 1:
The system performs preliminary actions by detecting power loss events early and initiating a controlled shutdown sequence before the actual power is cut. The PMU detects the event, changes status signal states, and systematically powers down functional blocks in the correct sequence, allowing pending operations to complete and data to be preserved, thus avoiding interruptions that would cause errors
2Reliability
If the system waits for all active operations to complete before transitioning to power-down state, then system reliability is improved, but the response time increases
Solution Approach 1:
The system dynamically adjusts the shutdown process by monitoring the state of active functional blocks and adapting the power-down sequence accordingly. The PMU changes status signal states to indicate different phases of shutdown, allowing the system to balance between completing necessary operations and transitioning to power-down state efficiently, thus minimizing unnecessary delays while ensuring reliability
3Use of energy by moving object
If voltage is reduced immediately upon detecting power loss event, then energy consumption is reduced, but non-volatile memory programming operations are interrupted causing errors
Solution Approach 1:
The system performs preliminary actions by detecting power loss events early and initiating a controlled shutdown sequence before the actual power is cut. The PMU detects the event, changes status signal states, and systematically powers down functional blocks in the correct sequence, allowing pending operations to complete and data to be preserved, thus avoiding interruptions that would cause errors
Solution Approach 2:
The system provides beforehand cushioning by implementing a controlled shutdown sequence that buffers the abrupt power loss event. The PMU manages the transition by progressively reducing power to different blocks, cushioning the impact on sensitive operations like memory programming, and allowing time for data to be safely written or cached before power is fully removed
4Stability of the object's composition
If the system enters reset state immediately, then system stability is restored, but volatile memory data is lost
Solution Approach 1:
The system performs preliminary actions by detecting power loss events early and initiating a controlled shutdown sequence before the actual power is cut. The PMU detects the event, changes status signal states, and systematically powers down functional blocks in the correct sequence, allowing pending operations to complete and data to be preserved
Data Source
AI summary
In an embodiment, a system includes a power management unit (PMU), a non-volatile memory, a volatile memory, and a processor. The PMU may be configured to generate a power supply voltage, change a state of a status signal responsive to an event, and reduce a voltage level of the power supply voltage responsive to a predetermined period of time elapsing from detecting the event. The system may be configured to transition from a first to a second operating mode responsive to the change of the state of the status signal, and cancel pending commands to the non-volatile memory responsive to the transition to the second operating mode. The non-volatile memory may be configured to complete active commands prior the predetermined period of time elapsing.