19.3 Power requirements for wearable devices

Wearable devices need to be small and lightweight, which means their power sources are limited. This section dives into the power requirements for these gadgets and how to make them last longer on a single charge.

We'll look at low-power components, smart design strategies, and clever power management techniques. These approaches help wearables do more with less energy, making them practical for everyday use without constant recharging.

Microelectronics and Sensors

Low-Power Components for Wearables

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Top images from around the web for Low-Power Components for Wearables

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  ATtiny402 Timer with low power sleep mode - Electronics-Lab.com View original

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• 

  SensorTile, An Accurate Development Kit For Biometric Wearables - Electronics-Lab.com View original

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• 

  SensorTile, An Accurate Development Kit For Biometric Wearables - Electronics-Lab.com View original

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  ATtiny402 Timer with low power sleep mode - Electronics-Lab.com View original

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  SensorTile, An Accurate Development Kit For Biometric Wearables - Electronics-Lab.com View original

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• Micropower electronics consume minimal energy while performing essential functions in wearable devices
• Low-power sensors detect and measure physical phenomena using minimal energy (accelerometers, heart rate monitors)
• Energy-efficient microcontrollers process data and control device operations with reduced power consumption
• Ultra-low-power sleep modes allow components to enter dormant states when not in use, conserving energy
• Subthreshold operation enables circuits to function at voltages below the typical threshold, reducing power requirements

Design Strategies for Power Optimization

• Circuit miniaturization decreases power consumption by reducing parasitic capacitances and resistances
• Dynamic voltage and frequency scaling adjusts processor performance based on workload, optimizing energy usage
• Power gating techniques disconnect unused circuit blocks from the power supply, eliminating static power dissipation
• Asynchronous logic design removes the need for a global clock, reducing power consumption in idle states
• Energy harvesting integration allows devices to scavenge power from ambient sources (body heat, motion)

Power Management

Power Budgeting Techniques

• Power budgeting allocates available energy resources among various components and functions of a wearable device
• Duty cycling schedules active and sleep periods for different components to reduce overall power consumption
• Dynamic power management adjusts system performance based on real-time workload and battery status
• Power profiling analyzes energy consumption patterns to identify and optimize high-drain operations
• Adaptive algorithms adjust device functionality based on remaining battery life, prioritizing critical functions

Energy Storage Considerations

• Battery capacity requirements depend on device functionality, usage patterns, and desired operation time
• Energy density of batteries impacts the overall size and weight of wearable devices
• Rechargeable lithium-ion batteries offer high energy density and multiple charge cycles for long-term use
• Solid-state batteries provide improved safety and energy density for next-generation wearables
• Supercapacitors enable rapid charging and discharging for applications requiring bursts of power

Communication and Display

Wireless Communication Power Optimization

• Low-power wireless protocols (Bluetooth Low Energy, Zigbee) reduce energy consumption for data transmission
• Adaptive transmission power control adjusts signal strength based on distance and interference levels
• Data compression techniques reduce the amount of information transmitted, lowering power requirements
• Opportunistic communication schedules data transfers during optimal network conditions to minimize energy use
• Wake-up radio systems allow devices to remain in sleep mode until a specific signal is received, conserving power

Energy-Efficient Display Technologies

• E-ink displays consume power only when updating content, ideal for low-refresh-rate applications (smartwatches)
• OLED displays offer pixel-level control, allowing partial screen updates and true blacks for power savings
• Transflective LCD screens utilize ambient light to enhance visibility, reducing backlight power consumption
• Ambient light sensors adjust display brightness automatically, optimizing power usage based on environmental conditions
• Low-power display drivers and controllers minimize energy consumption during screen operations