Design Of A Peak Current Mode Synchronous Step-down DC-DC Converter XD2121

Due to power is the basis for the normal operation of electronic equipment products, as demand for electronic equipment market is growing, the power supply performance requirements are also increasing. Since the advantages of switching power supply are small, lightweight, high performance and high efficiency, it has been widely applied to various fields, in such a market demand background, this paper designs a peak current mode synchronous buck DC-DC converter.Firstly, this paper introduces the development history and future trend of switching power supply, followed by a detailed presentation of the pros and cons of switching power supply, and then, based on the basic principle of switching power converters detailed analysis of the three DC-DC converter topologies(buck type, boost type and buck-boost type) and works are given, while the buck converter control modes(voltage mode control, peak current mode control) are explained deeply, and the modulations(PWM and PFM) of DC-DC converter are made a brief introduction, then, combining the current social requirements and laboratory projects, electrical characteristics and performance of the chip are designed, and the sub-module functions of the chip are made a brief introduction, and the stability problems and solutions of the system are analyzed deeply when the buck converter uses peak current mode. Secondly, some sub-chip modules are analyzed in detail, in order to improve the readability of the chip, the chip increases POWERGOOD module, allowing users to understand the chip directly whether it works properly or not, and in order to avoid the impact of feedback voltage fluctuations on the output, the 30 ?s delay is designed. At the same time, the chip increases the HICCUP module, it is triggered when the system is shorted, and then the chip enters HICCUP mode to avoid the chip device to be damaged, and the chip can resume normal work quickly when the system is not shorted. By adding these modules, the chip has a high readability and reliability. Finally, the paper gives the overall simulation and the layout of the chip, the test circuit and simulation results of full, no-load, short circuit and load step response are introducted, and its performance is in line with the designed performance of the chip. At the same time, the paper introduces two kinds of layout technologies(the symmetry and the reference source), and gives the overall pattern of the chip.Chip XD2121 uses PWM modulation to achieve high efficiency with wide load, uses peak current mode control loop to achieve fast transient response, uses continuous conduction mode to achieve low output voltage ripple, integrates power tube to achieve synchronous rectification, uses ramp compensation circuit to achieve stability of the current loop, and integrates multiple protection circuits, such as over-temperature protection, undervoltage latch loop, POWERGOOD etc., to improve security of chip devices, and promote reliability and readability of the chip.Chip XD2121 described in this paper uses 40 V BCD process, and uses Cadence and Hspice to simulate each sub-module and the overall circuit, and simulation results show that the performance of the chip can meet the requirements designed, and can be very good to achieve the desired function.