Proving the Business Case for the Internet of Things

Ambiq and PixArt combine to develop heart rate monitor for wearables

Steve Rogerson
March 2, 2016
At last week’s Embedded World in Nuremberg, Texas-based Ambiq Micro and Taiwanese company PixArt Imaging announced they had partnered to develop an ultra-low power heart-rate monitor (HRM) for deployment in next-generation wearable products.
The fast-growing wearables market is rapidly evolving from devices that are primarily fitness-oriented to those that are intended to provide more sophisticated data and information on the health and wellbeing of users. As a result, continuous heart-rate-monitoring functionality is increasingly becoming a key requirement for these types of devices. This presents a huge challenge for wearable developers in balancing the limited battery resource available on wearable devices and the need for continuous HRM.
The joint development from PixArt and Ambiq enables the always-on sensing functionality for makers and OEMs looking to deliver the next generation of product for wearable health and wellness applications. Delivering a consumption of less than 350µA total power in continuous operation, it combines Ambiq’s Apollo ARM M4 with floating point unit MCU, which acts as the main processor, with PixArt’s CMOS-sensor-based heart rate monitor family.
“PixArt’s vision and commitment to the wellness market is deeply rooted from our proven CMOS optical sensor in HMI,” said Sen Huang, CEO of PixArt Imaging. “The 800X HRM sensor family represents incredibly small packaged solution, ultra-low power and rapid deployment for the wearable markets.”
PixArt’s HRM sensor deploys the photoplethysmogram (PPG) technique, which transmits LED light waves into the skin of the user and measures the response change caused by absorption due to pulsating arterial blood. Outputting captured PPG data from the user, these measurements can be used to monitor heart rate and stress levels.
“Until now, always-on heart rate monitoring has been a much talked about feature but one that is not practical to implement due to the large amount of power it consumes,” said Keith Odland, senior director of marketing at Ambiq Micro. “By utilising our best-in-class hardware paired with highly optimised software, Ambiq and PixArt have achieved HRM power consumption levels that are not only one of the best in the industry, but deliver on the promise of always-on HRM.”
Based on the 32-bit ARM Cortex-M4F processor core, in real-world applications the Apollo MCU delivers typically five to ten times lower energy consumption than competitive MCUs with comparable performance. This performance per watt can mean significantly extended battery life, which is critical for wearable electronics and battery-powered applications.
The reduction in energy consumption is achieved using Ambiq’s patented Spot subthreshold power optimised technology. In addition, the Apollo MCU optimises both active- and sleep-mode power, a technique that is claimed to be unique in the industry. The MCU consumes 34µA/MHz when executing instructions from flash memory and has average sleep-mode currents down to 140nA.
Headquartered from Hsin-chu, Taiwan, with offices in Silicon Valley, Japan and Malaysia, PixArt Imaging is a sensing and navigation company offering a broad selection of sensors and technologies to support complex human-machine interface designs. Founded in July 1998, the company specialises in CMOS image sensors, capacitive touch controllers and related imaging application development. It has experience in mixed-signal image processing design and systems development.