February 11, 2014 – Silicon Labs (NASDAQ: SLAB, Country Manager In-gyu Kim), a global leader in high-performance analog-intensive mixed-signal ICs, announced today the launch of the industry's first single-chip digital ultraviolet (UV) index sensor ICs (product names: Si1132/Si114x). These products are designed to be integrated into smartphones and wearable computing devices to measure UV exposure, heart rate/pulse rate, and blood oxygen saturation, as well as to perform functions such as proximity and motion control. The Si1132 and Si114x sensor ICs, a new addition to Silicon Labs' optical sensor family, are ideal for activity-measuring wrist/arm bands, smartwatches, and smartphone headsets. In addition to detecting UV indices, these devices can also provide health and fitness applications with the ability to detect nearby objects using ambient light and infrared (IR).

As developers seek to differentiate wearable and portable products with new features that protect people from UV exposure, the demand for UV detection in consumer electronics is increasing. UV detection is beneficial for individuals at risk of sunburn or those concerned about excessive sun exposure. Products equipped with UV sensors can measure cumulative UV exposure and sound an alarm before the end user reaches exposure levels that could harm their health while exercising outdoors. According to standards recommended by the World Health Organization (WHO), the digital UV index has a linear relationship with sunlight intensity and is weighted by the Erythemal Action Spectrum (EAS) developed by the International Commission on Illumination (CIE). This weighting provides a standardized measurement of the skin's response to different sunlight wavelengths, including UVB and UVA.

Traditional UV sensors combined a UV-sensitive photodiode with an external microcontroller (MCU), an analog-to-digital converter (ADC), and signal processing firmware. Silicon Labs has been the first to integrate all these functions into a single-chip solution within a very small 2 mm x 2 mm package, enabling a reduction in design footprint and BOM (and bill of material) costs. The UV sensor family includes the following devices.

• The Si1132 UV index and illuminance sensor is equipped with an industry-standard I2C interface to read digital UV index values.

• The Si1145/46/47 UV and IR proximity/ambient light sensors allow you to select one, two, or three built-in LED drivers and provide 15 selectable driving levels for motion detection.

When used in conjunction with an accelerometer, the Si1132 and Si114x sensors enable developers to implement standby mode tracking in wearable applications. Additionally, the sensor's ability to measure infrared and visible light levels allows for more effective control of the LCD backlight in environments with various light sources. As a result, it becomes an inexpensive and effective method to efficiently control the backlight to alleviate eye strain and reduce power consumption without distracting the end user.

The LED drivers in the Si114x sensors not only enable the implementation of touchless interfaces that allow end users to control the device without touching it from a specific distance, but also enable health and fitness tracking products to measure heart rate and blood oxygen saturation using light reflection. The Si1146, which provides two LED drivers, and the Si1147, which provides three LED drivers, enable motion and movement detection. The Si1146 can detect motion and touchless control along the z- and x-axis, while the Si1147 adds a third axis to detect three-dimensional motion. Both sensor products provide measured light reflections for post-processing to determine the type of motion.

The Si1132 and Si114x sensors deliver outstanding performance across a wide range of light sources, including direct sunlight. The robust sensing architecture includes an illuminance sensor capable of detecting light levels up to 128 kLux. The photodiode response and associated digital conversion circuitry demonstrate excellent immunity to flickering from artificial lighting and flutter noise from natural light.

The ultra-low power architecture of the UV index sensor enables thinner wearable designs with smaller batteries while extending battery life by utilizing a low average current of 1.2 µA for one UV measurement per second. These sensors provide superior sensitivity and a better detection range with significantly lower power consumption compared to competitors. The high IR sensor sensitivity enables longer battery life in motion/motion detection applications by using only 25.6 µs of IR-LED while having a detection range of 50 cm. Dynamic control of LED current further minimizes power consumption.

Mark Thompson, Vice President and General Manager of Access, Power, and Sensor Products at Silicon Labs, stated, “Wearable products require highly integrated, small-footprint, low-power sensing solutions, and we are meeting these demands by providing the industry’s first single-chip digital UV sensing sensor. This UV sensing sensor also offers ambient light and IR sensing capabilities for innovative health and fitness applications.” He added, “Silicon Labs is the only UV index sensor supplier that offers a wide range of other sensor products, including energy-friendly MCUs, wireless MCUs, and transceivers, that can be integrated for system solutions suitable for the rapidly growing wearable market.”

Silicon Labs provides wearable developers with comprehensive hardware and software tools to simplify the testing, characterization, prototyping, and software development processes. The UVIrSlider2EK UV/IR evaluation kit offers a state-of-the-art development platform suitable for Silicon Labs' optical sensors. Controlled by an ultra-low-power C8051F800 MCU, the UVIrSlider2EK connects two IR-LEDs from a Si1146 sensor and enables functions such as UV index measurement, advanced 2D/2-axis touchless motion detection, and object proximity detection. The UVIrSlider2EK is pre-configured with firmware that displays five levels of consumer UV intensity index using five LEDs. The demo software provides a GUI with an IR slider that displays the total UV index and detects left, right, and stop motions using eight visible LEDs. Additionally, Silicon Labs provides example software source code for illuminance, proximity, and motion detection algorithms.