Proving the Business Case for the Internet of Things

Maxim sensors could improve clinical accuracy of wearables

Steve Rogerson
August 6, 2019



California electronics company Maxim Integrated has introduced two health-monitoring sensors that are said to provide clinical-grade accuracy for wearables.
 
The Max 30208 clinical-grade digital temperature sensor enables wearable health and fitness use cases at half the power, and the Max M86161 in-ear heart-rate monitor provides a claimed best-in-class SNR at lowest power and 40 per cent less space for continuous heart-rate and SpO2 measurements
 
Designers creating wearable health and fitness applications can halve temperature measurement power with the 30208, as well as shrink optical product size by 40 per cent with the M86161. In addition, design engineers can improve sensitivity and accuracy.
 
To provide value, wearable health and fitness monitors require greater accuracy in measuring human biometrics such as body temperature and heart rate, but device designers have been limited by sensor accuracy for small, battery-powered, body-worn devices. These two continuous-monitoring body sensors provide higher degrees of accuracy in measuring vital signs such as temperature, heart rate and blood-oxygen saturation (SpO2).
 
The M86161 in-ear heart-rate monitor and pulse oximeter is said to be the market’s smallest fully integrated product that delivers accurate heart-rate and SpO2 measurements from hearables and other wearable applications. It is optimised for in-ear applications with its small package size and SNR – a claimed 3dB improvement with band limiting signal for PPG use cases compared with the closest competitor.
 
The M86161 cancels ambient light for greater accuracy and provides a Nyquist SNR of 89dB or 100dB SNR with averaging. In addition, Maxim provides algorithms for motion compensation to increase measurement accuracy.
 
This enables development of devices that cover a wider range of use cases. The M86161 delivers approximately 35 per cent lower power to extend battery life of wearables. In addition, an integrated analogue front-end (AFE) eliminates the additional AFE typically needed to procure a separate chip and connect to the optical module.
 
It has less than 10µA operating power typical at 25sps and 1.6µA in shutdown mode. The OLGA package measures 2.9 by 4.3 by 1.4mm. There are three LEDs –red and infra-red for SpO2 measurement and green for heart rate.
 
The 30208 digital temperature sensor delivers clinical-grade temperature measurement accuracy (±0.1˚C from +30 to +50˚C) with fast response time to changes in temperature. It also meets the power and size demands of small, battery-powered applications such as smart watches and medical patches.
 
The sensor simplifies the design of battery-powered, temperature-sensing wearable healthcare applications. It measures temperature at the top of the device and does not suffer from thermal self-heating. It is compatible with up to four I2C addresses to enable multiple sensors on the same IC bus, and it can be attached to either a PCB or a flex printed circuit.
 
It is available in a ten-pin LGA package measuring 2 by 2 by 0.75mm.
 
“Wearable devices continue to gain market traction, with global revenue now estimated to grow from $56.4bn in 2019 to $78.3bn by 2022 at a four-year compound annual growth rate of 13 per cent,” said James Hayward, principal analyst at IDTechEx Research. “Major growth drivers include additional value captured in the growth and evolution of products such as smart watches and ear-worn products, alongside the adoption of dedicated wearable devices in key healthcare verticals.”