Embedded Lab

ROHM Semiconductors presents this white paper on the Applications of Ambient Light sensors in Portable Electronics.

In portable electronic products, reducing the power consumption to provide the user with increased battery life is one of today’s critical design considerations. The liquid crystal display (LCD) and its associated backlighting are among the more (and frequently the most) power hungry loads in portable products. As a result, the use of an ambient light sensor (ALS) to optimize the operation of the backlight LEDs under a variety of environmental lighting situations is increasing while, at the same time, the preferred technology choices available to designers for sensing have shifted towards more integrated solutions. One very important application for ALS technology is cell phones. In a cell phone, the ALS enables automatic control of display backlight brightness over a wide range of illumination conditions from a dark environment to direct sunlight. With the ALS input, a microcontroller (MCU) or baseband processor increases or decreases the display brightness depending on the environment. This control dramatically improves visibility and reduces power consumption since LCD backlighting can draw as much as 51% of the power in the input standby mode.