Ambient light sensors offer low power, high sensitivity in a small package

By Heather Hamilton, contributing writer

Sensor solutions company ams recently introduced a series of new sensors designed to optimize brightness for smart home devices. The devices debuted at the Sensors Expo in San Jose, California, at the end of June, and offer low power and high sensitivity in a small package. Designed for consumer devices, the release includes the TSL2540 and TSL2541 ambient light sensors, as well as the TSL2740, which is a combined ambient light and proximity sensor.

The sensors can detect ambient light at an intensity as low as a few millilux. The sensors are designed to work in lighting conditions ranging from bright sunlight to a dark room and can automatically adjust LCD display backlighting or indicator LEDs based on the brightness of the ambient light.

Each sensor has separate photopic ambient light and infrared light sensing channels with interferometric IR and photopic filters deposited on the silicon. The company said that the photopic channel approximates the way that the human eye responds to different levels of light and very dark attenuated materials.

All three optical sensors are compact enough for consumer products in a QFN package that measures 2 x 2 x .5 mm. In addition, the TSL2541’s package is made with a special dark compound that ensures that the device is nearly undetectable mounted under inked cover glass, said the company.

The TSL2740, which is also a proximity sensor, does so by measuring reflected IR light that comes from an external LED. Because it is also equipped with programmable proximity offset adjustability, it compensates for crosstalk effects from the IR LED in relation to proximity events up to 10 cm.

All three sensors are available in production volumes at $0.44 (TSL2540/TSL2541) and $0.46 (TSL2740) in quantities of 5,000. For a complete list of specs, including datasheets, look here .