Design Of 36 - Channel Constant Current Led Driver Chip

This thesis researches and developments for low-lighting application of LED driver,mainly applied in mobile phone, MP3and other low-lighting portable devices withLED backlight. According to the characteristics of LED, designed the innovativeLED driver chip with36-channel respiratory. The output current of36-channelmatched accurate, and the chip area is smaller. Adopt a simple external circuitsbuilding, the chip that could be form the colorful backlight.Firstly, we select the0.35μm5V low-voltage CMOS mix-signal process by CSMCInc., carefully analyzing and calculating the carrying voltage, output current andpower consumption of LED driver, to make sure that the chip runs under the processsafety, and proposing this chip design solutions.Secondly, analyzing the applications of LED driver, adopting constant currentsource-driven architecture, designed the36-channel constant current LED drivercircuit. Using PWM dimming and analog dimming technology, combined with I2Cinterface for data communication and control. Then, the chip could put out a varietyeffects by writing code, making the application flexible and diversified. For theproblem of digital adventure competition during PWM dimming, the innovativedesign of the PWM dimming logic circuits avoid the glitches.The chip would produce electromagnetic radiation (EMI) when multi-channelworking at the same time. Here, we delay2ns in each channel to reduce EMI for thefirst time.Design the electromagnetic compatibility (EMC) for the requirements ofapplication. We proposed EMC output stage circuit, so that in the EMI environment,the LED couldn’t flicker.Finally, the product using CSMC process of2P3M/0.35FEOL/0.5BEOL/5V,finishing all the circuit design, simulation, layout design and MPW tape out. Theproduct can meet all the design spec in the final testing and meet application withcustomer. It has outstanding performance, so it can be adapt to use in mobile phone backlight.