Ultralow-Power Sensor Hub Using Frequency-Locked Loop Clock
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Solution Overview
Problem
Traditional wearable devices consume high power due to continuous operation of the main central processor unit (MCU) and phase-locked loop (PLL) during sensor polling, leading to inefficient energy management and potential latency issues when switching between active and sleep states.
Innovation Solution
An ultralow-power sensor hub that employs a frequency-locked loop (FLL) to generate a low-power clock signal, shutting down the crystal oscillator and PLL during polling periods and using a low-power oscillator to manage sensor activity detection, thereby reducing power consumption and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main central processor unit (MCU) and phase-locked loop (PLL) operate continuously during sensor polling, then reliable sensor activity detection is achieved, but power consumption increases significantly
Solution Approach 1:
The system segments the processor functionality by separating the main central processor unit (MCU) from a dedicated sensor hub. The sensor hub handles sensor polling and activity detection independently, allowing the MCU to enter low-power states while the sensor hub remains active with reduced power consumption. This segmentation enables reliable sensor monitoring without requiring the full power of the main processor continuously.
Solution Approach 2:
The sensor hub extracts and handles the specific function of sensor polling and activity detection separately from the main processor. By taking out this specific function and dedicating it to a separate low-power unit, the system achieves reliable sensor monitoring while the main processor can conserve energy by operating at lower power states or entering sleep modes between polling cycles.
2Speed
If the sensor hub switches quickly between active and sleep states, then timely sensor activity detection is achieved, but latency issues occur during state transitions
Solution Approach 1:
The sensor hub performs preliminary actions by maintaining a ready state with essential functions active while the main processor is in sleep mode. The sensor hub pre-processes sensor data and maintains polling capabilities during the main processor's low-power periods, so when the main processor wakes up, it can immediately process sensor activities without additional latency from cold starts or full system initialization.
Solution Approach 2:
The system implements periodic sensor polling by the sensor hub at optimized intervals, allowing the main processor to enter sleep modes between polling cycles. This periodic action pattern enables timely detection of sensor activities while minimizing the time the high-power main processor remains active, thus reducing overall latency while managing power consumption effectively.
3Measurement precision
If sensors are polled repetitively every 50 ms, then accurate activity detection is achieved, but power consumption increases due to continuous processor operation
Solution Approach 1:
The system segments the polling function from the main processor and assigns it to a dedicated sensor hub operating at lower power. This allows repetitive polling every 50 ms to continue with accurate activity detection, while the main processor remains in low-power states between polling cycles, thus maintaining measurement precision without the continuous power consumption of full processor operation.
Solution Approach 2:
The sensor hub performs self-service by independently handling sensor polling, data collection, and initial processing without requiring the main processor to be continuously active. The sensor hub autonomously manages the repetitive polling every 50 ms, maintaining accurate activity detection while the main processor conserves energy by operating only when sensor activities are detected or during periodic data synchronization.
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 significantly reduces power consumption during polling periods, maintaining low power usage while ensuring timely detection of sensor activities, thus enhancing the energy efficiency and performance of wearable devices.
Implementation Method 1
a frequency-locked loop (FLL) to generate a low-power clock signal
Implementation Method 2
its associated phase-locked loop (PLL)
Data Source
AI summary
A system includes a frequency-locked loop (FLL) circuit, a sensor-hub circuit and a processor. The FLL circuit is used to generate a low-frequency clock. The sensor-hub circuit is coupled to a number of sensors and is configured to periodically poll the sensors during polling periods and to detect sensor activities. The processor is coupled to the sensor-hub circuit and can process sensor signals from one or more active sensors. The processor is off during polling periods and is turned on when a sensor activity is detected. The polling periods are based on the low-frequency clock generated by the FLL circuit.