Optical sensors for a new class of wearables

In 2014, Silicon Labs introduced the Si1132/4x sensor series, the industry’s first single-chip, digital sensor ICs for measuring the ultraviolet (UV) index. With models that combine UV, IR, and visible light sensing, the chips will let mobile and wearable devices track UV sun exposure and monitor heart/pulse rate and blood oximetry, while providing proximity/gesture control.

While the sensor combinations obviously open new possibilities for optical sensing, each sensor’s performance is also outstanding. Under a wide dynamic range of light sources, including direct sunlight, the ambient light sensor is capable of sensing light levels (up to 128 kLux) while providing excellent noise immunity to artificial light flicker and natural light flutter. Consuming as little as 1.2 mA on average for once-per-second measurements, the UV index sensor's ultra-low-power architecture extends battery life, enabling thinner wearable designs with smaller batteries. And the IR sensor’s high sensitivity provides significantly longer battery life in motion sensing/gesture applications, requiring use of just a single IR-LED with 25.6 µs on-time while enabling up to 50 cm sensing range.