Wide dynamic range light sensor for display and non-display applications

April 17, 2013 // By Christoph Hammerschmidt
ams has introduced a digital light sensor family that offers low-light sensitivity down to 0.000377 lux with a 600M:1 dynamic range up to 88,000 lux, equivalent to bright sunlight. The TSL2591 device family increases design flexibility and offers engineers new levels of performance in ambient light sensors for displays, as well as for a wide range of non-display applications.

Designs using lower-sensitivity light sensors face constraints and are forced to meet tight specifications governing the properties of the attenuating material they are placed behind, the physical placement of the sensor, and the minimum intensity of light needed to deliver sufficiently accurate measurements. The TSL2591 device family gives greater flexibility in system design and layout. Its high sensitivity and wide dynamic range mean that it can deliver accurate measurements even under very low light conditions. This gives the designer the freedom to place the sensor away from the direct path of the light it is measuring and behind a wider variety of darkened glass or attenuating materials.

For display applications, the light sensor TSL2591 device family uses an ams dual-photodiode architecture that provides accurate ambient light measurements even when placed behind material attenuating as much as 99% of the visible light while automatically compensating for the increased IR component. This enables a photopic response to ambient light intensity that mimics the human eye. Its high sensitivity reduces or eliminates design concerns for smartphone and tablet displays in which inked glass variations can result in costly design alterations to accommodate less sensitive devices. The TSL2591 can be placed deeper within the end product, providing more efficient and lower-cost solutions which offer the product designer more flexibility from a system design perspective. It also provides for a sleek, seamless industrial design with no unsightly apertures or voids in inked glass.

In addition, the TSL2591 device family provides an interrupt feature that simplifies and improves system efficiency by eliminating the need to poll a sensor for a light intensity value. The primary purpose of the interrupt function is to detect a meaningful change in light intensity. Meaningful change can be defined by the user in terms of light intensity and time, or the persistence of a change in intensity. TSL2591 is an integrated light-to-digital sensor with dual analog-to-digital converters and an I 2