| In today’s world, people’s life, work and social development have been inseparable from the electronic devices consisting of electronic equipments. Especially, power management chips have a wide range of applications. In this thesis, according to the function, the actual typical application circuit and electical characristics of the chip, a high efficiency synchronous buck DC-DC converter with a constant frequency XD1436 is designed systematically after a detailed theoretical analysis.In this thesis, firstly, the background and the development status of power management chips development are described in detaile. In considering the population, energy, environment and other factors, this paper makes the prospects for its development trend based on the summary of the characteristics of switching power supply technology. There is a detailed description of the technology related and the main characteristics parameters as well. As this chip XD1436 is a kind of buck DC-DC converter, BUCK, BOOST and BUCK-BOOST DC-DC converter are analyzed and derivated in detail. After this, based on comprehensive consideration of the chip function, the practical application and the level of technology, the chip’s main electrical characteristics and the control mode are selected, then the overall circuit of the chip system is designed.Combined with the function and operating principle of the overall chip, the chip XD1436 is design systematicly. Based on the chip’s practical application, the chip’s key sub-circuits, ENABLE, UVLO, VREF, OSC, SLOPE, EA, PWM, OTP, Soft_Start, LOGIC and other modules are designed and analyzed. Each module and the overall circuit are simulated in typical condition in this thesis. The conversion rate of the chip is improved by using synchronous rectification technology. Instead of an external Schottky diode with a MOSFET, PCB board area is reduced. The chip is designed with a wide range of input voltage which is from 2.7V to 5.5V. 3A maximum output current makes the chip become an ideal chioce of a portable notebook, LCD TV, set-top boxes or other electronics applications. 100% duty cycle makes the chip achieve a low dropout voltage which extends the battery life in portable systems. Low output voltage and internal smaller mount inductors and capacitors make the chip receive a high constant switching frequency of 1MHz. And a linear slope compensation technology is introduced to effectively avoid sub-harmonic oscillation phenomena. Under Voltage Lockout(UVLO), Over Voltage Protection(OVP), Over Current Protection(OCP) and Over Temperature Protection(OTP) are designed to shut down the chip when it works abnormally. Those protection modules improve the reliability of the chip. Simple voltage divider structure is uesd to obtain a feedback reference voltage of 0.6V. Soft_Start function module is designed to prevent damage the device during the startup time because of the inrush current and overshoot voltage.Detailed theoretical analysis of the system and key sub-circuits of XD1436 are made in this thesis. Based on 0.5 mm COMS process, the schematic design and pre-layout simulations and verifications have been completed using Cadence. The simulation results turn out to be that all the functions have been implemented and electrical characteristics are consistent with the design specification. And the design of internal synchronous rectification technology, Soft_Start, Under Voltage Lockout(UVLO), Over Voltage Protection(OVP), Over Current Protection(OCP) and Over Temperature Protection(OTP) modules and internal smaller inductors and capacitors have improved the reliability of the chip XD1436. |
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