Design Of Light Sensor XD1216Based On Human Eyes Sense

In improving the human visual experience, the light sensor has become one of themost effective solutions. To any product with a display, it will be not easy to use whenambient light changes. The requirements of people change with environment changing.In the bright outdoor areas, the human eye can adapt to the same brightness withambient light, but indoor or night, the relative brightness of the display appears toobright for the human eye, and even some glare. So if you do not manually change thesystem settings (usually in terms of the brightness control), then the display will notonly consume the same amount of energy, but also reduce the user experience.This article about the Light Sensor XD1216which is designed based on humansense is a good solution to these problems. Ambient light can be collected by lightsensor XD1216and sent back to microcontroller, so the brightness of display will adaptthe changing in ambient light. As we all know, Ambient light includes not only thehuman eye visible light wavelengths, but infrared light and others which are invisible.This design adopts two photodiodes, one group is capable of sensing visible andinfrared light, and the other group can sense infrared light. Visible light can be accurateby subtracting of the light sensed by two photodiodes. A charge-balanced ADC is adoptto achieve digital output of the sensor, and the light data collected is sent to the externalmicrocontroller through the I2C bus.Upon analysis of the working principle and system design of Light Sensor XD1216,each module and the overall circuit were designed and simulated based on0.35umCMOS process, using Cadence Spectre. Simulation results show that, XD1216has agood ambient light data collection and accurate conversion from analog to digital. Theperformance achieves the desired design requirements.