| Power supply is an indispensable part in application electronic equipments such as TV, computer and portable communication equipments, which is the fundamental requirement for normal operation. Switch mode power supply, with its compact volume, small weight, high efficiency and good line regulation, has been widely applied in most of electronic fields. The core of switch mode power supply is integrated IC control system. Its high integration level, quality-price ratio and efficiency make it become the major candidate for application power design.In recent years, the portable electronic products is becoming more and more popular, which makes a rapid growth of power management IC. With the purpose of providing more functions and high performance, as far as saving energy, these electronic products need switching power supply chip with high conversion efficiency and high precision.This thesis proposes a high precision monolithic buck DC-DC converter. The chip adopts the voltage PWM control mode, and uses decreasing frequency protection. In the chip, a digital controlled soft-star circuit is contained. This chip is characterized by high precision, high converting efficiency and small strike-voltage and surge-current at starting stage.Spectre simulations are done on each cell and the whole system in cadence with the parameter of HHNEC 0.35um BCD process. It works at 4V to 12V supply voltage, and provides 1.8V to 6V output voltage with a maximal output current of 1A. Simulation indicates that the output ripple is only 2mV, the output precision is 0.05%, and the power efficiency is above 90% with 5V supply voltage, 2.5V output voltage and 5? load resistor. Also in other typical simulations, the respective values are achieved. |
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