A system containing an ambient light and a proximity sensor with intrinsic ambient light rejection

A system for measuring ambient light as well as proximity of a reflective object is presented. A new technique of ambient light disturbance cancellation in proximity mode is proposed, enabling high accuracy measurements over a wide range of backlight. The chip, built in a 0.25μm CMOS technology, is capable of measuring ambient light intensities with a resolution better than 0.25lx at a 16klx full-scale and a reflected proximity IR signal with amplitude down to 200pA, rejecting backlight variations from 0 to 100μA.