FEATURE COVER STORY
THE ERA OF SMART WEARABLES: Enhancing the user experience
Steve Knoth, senior product marketing engineer of power products at Linear Technology Corporation (now part of Analog Devices Inc.) looks at how ultralow IQ
ICs are effectively powering smart wearable devices, creating something of a revolution in this technology trend F
rom Google Glass to advanced fitness activity trackers, to heads-up imaging
displays to blood pressure monitors, wearable devices have entered the military, industrial and high-end consumer markets. These devices are rapidly improving and becoming even “smarter.” A “wearable” can be defined as a product that is worn by the user for an extended period of time and in some way, enhances the user’s experience as a result of the product being worn. A smart wearable adds connectivity and
independent processing capability to the device. It is estimated that the wearables market will grow to 130 million units by 2018 [Source: PwC, October 2014]. Wearables are divided into five application sub-categories: fitness/wellness (activity monitors, fitness bands, foot pods and heart rate monitors), healthcare/medical (pulse oximeters, hearing aids and blood pressure monitors), infotainment (smart glasses/goggles, smart watches and imaging devices), military (heads-up displays, exo-skeletons and smart clothing), and industrial (body-worn terminals) [Source: IHS Electronics and Media, 2013]. These categories have different market forces driving their adoption rates. In the wellness and medical segments, these include: rising life expectancy, the desire to prolong a healthy life and to reduce hospital stays. For military, it’s the desire to improve situational awareness, maps/routes, combat efficiency and save lives. For industrial, the main drivers are improving production line efficiency and tracking capability. Finally, for infotainment, the exploding gaming market with cutting edge imaging and virtual reality, as well as the increasing number of devices able to connect wirelessly to smart phones to become part of the “internet of things”.
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speaking, the core architecture for a smart wearable is a combination of the following: a microprocessor or microcontroller or similar IC, some sort of micro-electromechanical sensors (MEMS), small mechanical actuators, Global Positioning System (GPS) IC, Bluetooth/cellular connectivity, imaging electronics, LEDs, computing resources, battery or battery pack, and support electronics. A wearable unit’s primary goals are to
Figure 1: Sho
have a compact form factor, low weight for wearability/comfort and provide ultralow energy consumption in order to extend battery run time. Wearables are obviously “cool” products - however powering them efficiently and accurately while charging batteries with minimal current draw - is another matter entirely. Some of the key issues associated with powering smart wearables with ICs include the following: Low current consumption from the IC in a battery-powered device is paramount for increased run time. A micropower – or even better a nanopower – conversion IC is ideal.
SMART WEARABLES ARCHITECTURE & PROBLEMS So, what’s “under the hood” of your smart wearable device? Think of it as a miniature embedded system. The exact partitioning will obviously depend on the device itself. However, generally
Figure 1: LTC3388-1/-3 typical application circuit
Some wearable device architectures use a multiple-battery approach, for example, 2 x Lithium 8.4V battery rather than a single-cell Lithium (4.2V). This increases capacity and gives longer system run time. However, a higher voltage IC is then required.
A MEMS sensor requires power from a quiet regulated power source. Busy
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