| With the purpose of providing more functions and high performance in the portable electronic products, protecting the environment, as far as saving energy, the switching power supply chip with high conversion efficiency is needed. A high efficient and high integrated DC-DC converter has been designed to meet the application requirements.The chip is a 500k synchronous rectified buck DC-DC converter with built in internal power MOSFETs. It is cable of driving a 3A load with high efficiency, excellent line and load regulation. The current mode control provide fast transient response and cycle-by-cycle current limit, the internal optimized compensation network make the loop easy to design. The protection features include soft-start(SS), UVLO, thermal shut down(OTP) to protect the cicuit.In this paper, the main function modules of the converter includes: bandgap reference circuit, regulator, error amplifier, compatator, oscillator, current sense circuit, enable circuit, soft start circuit, under voltage lock out circuit, over temperature protection, and bootstrap circuit. Meanwhile, simulation researches are done for each cell in cadence and prospective value is achieved. Based on the application circuit of the converter, the tests are accomplished by the simulation software Hspice. The results show that all of the electrical characteristics can meet the specifications. The efficiency of the converter reaches 95%. It can be used in notebook systems, Digital Set Top Boxes and so on.The design chip has been taped out with a BCD process, the corresponding layout area is 1.5mm×1.5mm. |
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