| With the wide use of portable devices, the application of lithium battery has become more and more widely. Therefore, the demand for lithium battery charging management chip is also becoming more and more important. A good power management chip can save time and protect the lithium battery to prolong the life of the lithium battery.And now a lot of portable devices are supporting the function of OTG USB, so the power management chip is also more and more functional requirements.In this thesis, we study the design of a lithium battery charging chip, the chip charger combines with a highly integrated switch-mode of a synchronous buck regulator and a On-The-Go USB(OTG) peripheral to provide 5V power supply synchronous booster regulator. A current mode PWM/PFM modulator is used to adjust the output voltage and the battery charge current. And the I2 C bus specification is compatible with and control the working mode and working parameters of the chip, including charging, boosting and high resistance mode. The design is based on the CSMC 0.5 um BCD technology platform.The chip can be programmed through the I2 C interface to control the conversion of the chip operating mode. Both can be powered by an external USB power supply(that is, charging mode), while the internal also contains a boost regulator, so that the chip can be charged separately for the USB device(that is, the boost mode). The chip is concluded with over temperature protection, under voltage blocking(to prevent excessive power consumption), over voltage protection(to prevent excessive charging) and other protective functions, to ensure the safety of the chip.This thesis mainly introduces the overall structural design according to the demand of the chip, and focuses on the several sub-modules of my work, including: band-gap reference circuit, PWM comparator circuit, over temperature protection circuit and over-voltage protection circuit. Simulation results are appropriate to achieve the system requirements. |
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