Balancing Good Health with Good Design
Sensor processing SoCs and low power AFEs are examples of devices determined to make a smaller, lighter and more wearable difference for consumers.
We are familiar with heart rate monitors, glucose meters, even calorie counters and activity trackers, to bring healthcare to the individual. As well as saving costs, they offer convenience, shorten a stay in hospital stays, and add the convenience of remote health checks from home.
Low power consumption is still a significant design criteria, as these devices are always-on, and usually in wearable formats, for example a wristband or a chest strap.
There have been many introductions to create smaller, lighter, wearable heath devices that address the issues of cost and convenience. This month, Analog Devices introduced a low power, biopotential analog front end (AFE). Designed to reduce the size and weight of cardiac monitoring devices, as well as making them less obtrusive, the AD8233 extends battery life for longer, uninterrupted use and low maintenance requirements.
The integrated, single-lead electrocardiogram (ECG) front end reduces development time. Developers do not have to collect and assemble individual components. It measures 2.0 x 1.7mm in a Wafer Level Chip Scale Packaging (WLCSP) and operates from a single 1.7 to 3.5V supply. Quiescent current is just 50μA (typical). Of particular importance in cardiac monitoring, electrical noise is below 10μV from 0.5 to 40Hz.
Typically, data from more than one sensor is collected in wellness and fitness devices. A sensor hub collects, interprets and makes the data meaningful to the device.
Low power consumption is a significant design criterion for devices that are always-on and usually in wearable formats, for example a wristband or a chest strap. QuickLogic is one company tackling power consumption, with the ArcticLink 3 S2, the Customer Specific Standard Product (CSSP) sensor hub. Standard and low-power (LP) variants reduce power consumption in an always-on, contextual awareness environment.
Active power consumption is 93µA at 1.2V, or 76µA at 1.2V, and 68µA active power at 1.1V for the ArcticLink 3 S2 LP version. This meets the two percent power consumption threshold that Original Equipment Manufacturers (OEMs) are chasing for always-on, context-aware devices. It also exceeds, says the company, the typical options of embedding a sensor inside an application processor or as a discrete microcontroller, consuming up to 10 and six percent of battery life respectively.
When combined with the company’s SenseMe algorithm library, the sensor hub allows the end device to track movement, speed of movement, and even mode of transport. Armed with this tracking capability, the device can relay information as to whether the wearer is in a vehicle, has been stationary for a long time, or has experienced sudden movement, e.g., a fall.
The company’s own, as well as third-party sensor algorithms, can be incorporated for particular application requirements.
The small sensor hub measures 2.2 x 2.5mm and is hardware and software compatible with an earlier sensor hub from the company, the ArcticLink 3 S1.
In August of this year, QuickLogic also began shipping the EOS S3 sensor processing SoC (Figure 2), for wearable, smartphone and IoT applications. The multi-core SoC enables concurrent sensor applications to add functionality such as voice triggering, motion-compensated heart rate monitoring, and indoor navigation sensor algorithms, without a power penalty.
The QuickLogic proprietary microDSP Flexible Fusion Engine operates at 30µW/MHz using an ARM Cortex M4F, with an active power consumption of 75µW/MHz. There are up to 2,800 effective logic cells and 578-kB of aggregate SRAM for code and data storage, all in either Ball Grid Array (BGA) or Wafer Level Chip Scale Packing (WLCSP).
The Mirror that Isn’t
New uses for wearable technology include smart-glasses to provide feedback for facial palsy sufferers when performing facial exercises. The smart-glasses are being researched by a team at Nottingham Trent University in the UK.
Facial Remote Activity Monitoring Eyewear (FRAME) glasses (Figure 3) monitor posterior auricular muscles. These are the muscles which control a person’s smile, FRAME glasses can also monitor the nasalis or medial orbicularis oculi, which control the nostrils, the corrugator procerus complex, which controls the upper nose and eyebrows, and the superior auricular muscles at the side of the head, which move the ear.
Exercise routines are delivered via a smartphone app, which also gives live feedback, data on muscle tone, and a weekly update on progress. Many patients do not like to use a mirror as a feedback mechanism. FRAME technology does not require a mirror, yet makes it possible for patients to receive feedback and incorporate vital recuperation exercises into their daily lives. Clinicians and patients are able to monitor progress with minimal disruption.
The $975,000 project is funded by the National Institute for Health Research Invention for Innovation Programme (NIHR i4i) and is being developed by a consortium led by Nottingham Trent University in collaboration with Queen’s Victoria Hospital, technology company Emteq, Coventry University, and the charity Facial Palsy UK.
Future uses, speculates the team, could be to provide feedback on mood, for example, to signal depression, or to enable someone who is tetraplegic to control a wheelchair.
Author. Caroline Hayes has been a journalist, covering the electronics sector for over 20 years. She has worked on many titles, most recently the pan-European magazine, EPN.