How can designers decrease power and increase functions in wearables: part 1

With their small size and minimal weight requirements, getting the right features at the lowest power consumption for wearable products is essential. Continuous power management improvements provide ongoing challenges. For maximum improvements to optimize the time between charges and/or battery life, as well as uninterrupted operation, all system aspects must be considered. In addition to the sensor(s), to collect, process, and transmit data, monitor sensors, update software, and more, data processing (including software and firmware), communications, power management, system algorithms, and other system aspects (including displays) are critical design considerations. Figure 1 helps visualize the power-consuming and feature-providing aspects of a typical wearable system.

Sensors

Depending on the type(s) of sensors, their operating time (activity per hour), and other factors, sensors in wearables can easily consume from a few to several mW or more. However, some sensors can consume as little as a few microwatts. For higher power-consuming sensors and to minimize the power consumption of any sensor, there are design tips that provide designers a means of achieving the desired operational objectives. These design tips include the choice of sensor technologies for the design, controlling the amount of time the chip is powered, how frequently readings are made, and other factors.

Data processing (plus instruction language)

The next power-consuming aspect of any wearable design is the computing or data processing portion. The microcontroller unit (MCU)/ system on chip (SoC) computing portion generally operates within 0.507 µW to 216 µW, is often optimized for lower power in sleep modes, and has other lower power operating modes. For operation with analog sensors, the data converters (ADC/DAC) portion of an MCU/SoC can require from 15 µW to 1.95 mW.

In addition to the computing hardware, the instruction language may play a key role in reducing power consumption and the ability to deliver more features. For example, one company’s line of digital signal processors (DSPs) features its Tensilica Instruction Extension (TIE) language that enables designers to move data significantly faster than conventional processors. This results in a more efficient and less expensive SoC implementation that consumes less energy. For wearable applications such as True Wireless Stereo (TWS) earbuds, hearing aids, Bluetooth headsets, smart watches, and more, a recently introduced DSP delivers an enhanced audio/voice experience for small battery-powered products.

However, computing can also be an integral part of devices dedicated to communicating the data.

Communications

Another essential design aspect is communicating or transferring the data from the wearable to another device for the user or others (such as a healthcare provider in medical applications or a safety/security analyst in industrial applications) to monitor. Wireless data transmission (using Wi-Fi, Bluetooth Low Energy (BLE), LoRa, or others) requires significant power in wearables because radios can consume several mWs while transmitting/receiving. As shown in Table 1, in addition to the choice of low-power wireless technology, the maximum operating distance and data rate are key factors to determine power consumption.

To improve the functionality of their low-power wireless connectivity products, semiconductor suppliers continually introduce new designs. For example, one supplier recently introduced the fifth addition to its next-generation series of wireless SoCs. It integrates a 2.4 GHz radio for low-voltage Bluetooth LE applications, a 128 MHz processor, a coprocessor, and essential peripherals to support a 1.2-1.7 V supply voltage range. In addition to providing a sub-50 nA system hibernation mode for shipping and storage, its power consumption is 30 to 50 percent lower in common Bluetooth LE use cases, compared to its predecessor.

References

Power Management in Wearable Electronics: Strategies for Longer Life and Smarter Designs
A Survey on Smart Wearable Devices for Healthcare Applications
Extending the Battery Life of Electronic Wearable Devices
Tensilica Instruction Extension (TIE) Language
New Tensilica HiFi 1 DSP delivers increased voice- and music-processing performance with optimal neural network capability in a compact footprint with ultra-low energy
Sensors, Batteries, and Low-Power Design for Wearable Devices in Medical Applications
Nordic Semiconductor unveils nRF54LV10A – a breakthrough low-voltage Bluetooth LE SoC for next-gen healthcare wearables

Related EEWorld Online content

Low-power sensor fusion platform seamlessly integrates into wearables
How can sensors save energy and improve sensor node battery life?
How can energy harvesting be used in industrial applications?