Design Of Dual Output Full Function Switching Mode White LED Converter XD8080 IC

With the increasing popularity of color liquid crystal displays in mobile phones, PDAs, digital cameras and other portable devices, white LEDs are becoming popular backlighting sources and white LEDs driving ICs are becoming the new highlight in the field of power management ICs design.This thesis is based on the project"Theoretical research and design of key technique for deep-submicron power management IC",on the basis of analyzing the working principles and designing requirements of white LEDs driving ICs, a dual output peak current mode Boost DC-DC white LEDs driving IC XD8080 is designed. Design process of XD8080 is described in detail, including definition of the IC specification, analysis of the electrical characteristics, implementation of sub-block circuits and simulation of the whole chip. The simulation of the sub-block circuits and whole chip has been completed, and the simulation results show that specifications are met.Two independent Boost converters capable of driving asymmetric LED strings are integrated in XD8080, which can independently achieve dimming and shutdown control of the two LED strings. XD8080 is an ideal choice to provide backlight for main and sub-displays in mobile phones and other portable devices. There are two different types of dimming control methods: one is using a variable DC voltage to adjust the LED current from 5mA to 20mA; The other method is using a variable duty cycle PWM signal to control the brightness of the LED string, the PWM signal is filtered by an RC network and fed to the CTRL pins. As a result of the adoption of peak current mode PWM control, the transient responses to the changes of both the supply voltage and the load become much faster. Over voltage protection, over current protection, over temperature protection and other protection circuits are designed, which make the system more reliable and stable.