An ultra low-power ambient light sensor for portable devices

摘要

Power management is one of the most important issues in portable electronics like cell phone, PDA, UMPC, GPS, MP3 player and laptop computer. Ambient Light Sensors are getting popular as a most effective solution to extend battery lifetime for these devices. This paper provides basic information about ambient light sensors on a general level and introduces an ultra low-power ambient light sensor for portable electronics. The implemented ambient light sensor converts light illuminance to 5-digital codes every 300ms which can measure illuminance from 10 to 1000 Lux consuming only 5uA. An IR-reject optical filter and a built-in integrating analog-to-digital converter reduce influences of infrared ray and 50Hz/60Hz noise from artificial light sources respectively. The ambient light sensor is fabricated in a standard CMOS 0.5-um process technology. Test results show that the implemented ambient light sensor has incandescent/fluorescent light sensitivity ratio around 2.3.