Digital Ambient Light Sensor XD1477 For Portable Devices

Portable consumer electronics, such as smart phones and tablet PCs, has become ?the breath of life‘ for modern people. However, short battery lifetime in portable electronics was always the hard nut to crack to manufacturers and criticized by consumers. For battery technology has no breakthrough, researchers hope to improve power efficiency. Ambient light sensors are getting popular as a most effective solution.Portable devices are widely equipped with high-definition display, whose backlight system is the most dominant power consumer. With ambient light sensors a portable device can automatically controll display luminance to improve power efficiency and extend battery lifetime. A portable electronics can adjust its display brightness to adapt to lighting conditions using data from ambient light sensors. The display will avoid dazzling users in low light or lack of brightness in high light, so as to provide an optimal user viewing experience.Based on smart sensor technology and photoelectric detecting technology, a digital ambient light sensor XD1477 is designed for portable devices in this thesis. First of all, applications, chip architecture and functional specifications are determined. Then the key modules are explained with theoretical analysis and circuit design. The functional verification is preceding using simulator hspice S in Cadence Virtuoso. Finally, the overall simulation in hsim shows electrical and optical specifications are met. The ambient light sensor has been fabricated in a standard 0.35 μm CMOS process.The implemented ambient light sensor converts optical signals into electrical signals by on-chip photodiodes, then into 16-bit digital codes by an A/D converter. Its spectral response is almost the same as human eye‘s photopic vision due to infrared rejection. The built-in integrating A/D converter can suppress 50 Hz/60 Hz noise from artificial light sources. Wide dynamic range and high sensitivity allows it to be applied to almost all of the lighting conditions. The ambient light sensor also features fast communication speed through I2 C interface, and a programmable interrupt output provided for minimal microcontroller utilization.