Vital sign monitoring for wearables

What is your resting heart rate, and is your blood pressure within range? 

Vital sign sensors have never been more smart, accurate and available. These biosensing technologies are implemented in wearable fitness trackers, watches and continue to expand into smart phones, earbuds, rings and even stick-on patches. 

Consumers use these products to optimize their health, fitness and lifestyle by monitoring their blood oxygen, heart rate, time asleep, respiratory rate, body composition, heart diseases and skin temperature - the list is growing. Wearable Bio-Impedance (Bio-Z) measures body composition, while Electrical Skin Activitiy (EDA) sensing tracks emotional effects on the body via sweat, both enhancing personal health monitoring. Clinicians and patients use medical grade wearable sensors to continuously and conveniently monitor the progression of medical conditions and therapies, delivering more personalized treatments with improved efficiency and clinical outcomes. 

ams OSRAM is unique in offering a complete portfolio of Light Emitting Diodes, Photodiodes, Optical Front Ends, Analog Front End ICs and temperature sensors to realize all of the above measurements. We support designers to rapidly realize complete, high performance, low power and small form factor vital sign monitoring solutions in their products.


All the key components in one place 

Optical vital sign sensors start with measuring Photoplethysmography (PPG) signals. An LED emits light into the skin, and an adjacent photodiode detects the variation in light absorption caused by blood flow changes. Capture of PPGs with multiple wavelengths further enables blood properties such as oxygenation to be derived. Algorithms are then applied to PPG signal(s) to derive key vital sign such as heart rate (HRM), heart rate variability (HRV) and blood oxygenation (SpO2). 

Electrical vital sign sensors amplify small voltage and impedance changes through electrodes that contact the skin, to derive signals such as electrocardiography (ECG), galvanic skin response (GSR) and Bio Impedance (Bio-Z). Temperature measurements can be further used to derive core body temperature. Bringing together all these sensor data, advanced algorithms may derive further metrics such as blood pressure, respiration rate, biomarkers like VO2 max, resting heart rate, or provide additional information such as fertility, body composition and recovery rate. 


Optical Front End (OFE) modules 

Placing LEDs and Photodiodes to achieve a high quality and reliable PPG signal is not easy.  Optical coupling of each to the skin must be maximized, but direct crosstalk minimized, and ambient light leakage prevented. High end products may deploy constellations of multiple LEDs, photodiodes and wavelengths to minimize the effects of user motion and derive more advanced signals. 

ams OSRAM Optical Front End modules integrate our high performance LEDs and Photodiodes. These are placed optimally for signal strength with appropriate optical isolation, ready to be placed into products that contact the skin.  

Using these Optical Front Ends, designers can deliver high performance PPG measurements with the minimum of complexity through both design and manufacture. 

Analog Front End (AFE)

Our state-of-the-art Analog Front End ICs comprise a one chip solution to derive high quality digital PPG, ECG and bioimpedance measurements directly from LEDs, photodiodes and skin electrodes.  

Integrated functions include LED drivers, photodiode read-outs, electrical signal amplifiers, sequencing across successive measurement pulses, analog to digital conversion and signal processing. Configuration and digital signal readout is provided to the processor over SPI/I2C.  

Our AFEs are specifically optimized for very high signal to noise ratios and offer numerous possibilities to improve the signal quality. They are further optimized for low power consumption, and available in small footprint and low height packages.  

This allows designers to create premium performance health and fitness monitors, in tiny form factors with multi-day intervals between battery recharges. For example, earbuds, fitness bands, smartwatches, sports watches and smart patches. 

Light Emitting Diodes (LEDs)

LEDs specifically designed for vital sign monitoring in power constrained applications. We offer LEDs in green, red, infrared and all relevant wavelengths. These deliver high conversion efficiency and low forward voltage, minimizing the drive current required, which enables designers to maximize the battery life of wearable products.  

Photodiodes (Light Sensors)

Photodiodes optimized for high-performance PPG measurements. Our latest Chip LED and TOPLED D photodiodes provide higher sensitivity and much higher linearity than standard photodiodes on the market today. Furthermore, our packages are optimized to maximize the photosensitive area within the package footprint and minimize visually distracting elements aesthetic integration.  

These enable designers to create premium products that deliver more accurate and reliable measurements, including under challenging ambient light conditions. 

Digital Temperature Sensors

ams OSRAM offers the world’s most accurate digital temperature sensor. The AS6221 is factory calibrated to deliver ±0.09° accuracy out of the box, over I2C, with no need for calibration or linearization. Best in class power consumption and a compact Waferlevel-Chipscale-package makes it ideally suited for use in wearable vital sign monitors.  

Body temperature is a vital sign that enables use cases such as fertility tracking. However, this requires close thermal coupling of the IC to the skin, which will apply mechanical stresses to the package. The AS6221 has best in class tolerance to mechanical stresses, enabling designers to reliably realize high accuracy skin temperature measurements in a variety of mechanical configurations. Read our press release about AS6221.

Algorithms for HRM, Sp02 and respiration rate

ams OSRAM offers algorithms to measure Heart Rate (HRM), Blood oxygen (Sp02) and respiration rate. Specially optimized to work with the PPG output from our LEDs, PDs and AFEs, and validated against CTA and IEC standards, these enable designers to rapidly create complete and high-performance vital sign monitoring solutions. 

Register for our white paper about vital signs monitoring in mobile and wearable devices

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