Silicon Labs' Si1132 and Si1145/46/47 are the first digital UV index sensors available in the market, enabling fitness wrist/arm bands, smart watches, and smartphones to differentiate by measuring UV sun exposure. Customers can benefit by receiving a warning of when their current UV exposure is unhealthy or to determine their cumulative UV exposure during exercise. This can be for people with an elevated risk of sunburn or anyone who is concerned about their sun exposure. The UV sensor calculates a digital UV index value using the CIE Erythema Action curve to provide WHO/EPA-compliant UV index across the full UV spectrum from UVA to UVB. The UV sensor outputs the digital UV index value through a standard I²C serial interface making it easy to integrate in a system with a tiny 2x2 mm QFN package.

This highly-integrated sensor family also enables sleep pattern tracking, proximity/gesture control, pulse rate measurement, and blood oximetry measurement. The Si1132 and Si1145/46/47 include an integrated ambient light sensor (ALS), enabling sleep pattern tracking when combined with an accelerometer that is typically used in fitness-tracking applications. The Si1145/46/47 adds a single-pulse proximity/gesture sensor and from 1 to 3 programmable LED drivers for improving the user interface. The proximity sensor also enables pulse rate and blood oximetry measurements when combined with host processing.

An innovative low-power integrated processing unit and sensor extends battery life. Si1132 average power consumption with once-per-second UV measurements is only 1.2 µA. The Si1145/46/47’s single-pulse proximity sensor minimizes the on-time of IR LEDs, the primary energy consumer of proximity/gesture detection, while eliminating the need for integrating multiple bursts to avoid fluorescent light flicker.