| This thesis mainly studies the design and implementation of BiCMOS DC/DC converters.Systematic design, circuit design, layout design and performance simulation of Buck DC/DC converter are comprehensively presented at first. Then, on basis of these analyses, the XD8183 that is a multi-mode high-efficiency buck DC/DC converter is fabricated. Because of adopting current-mode control in the design process, the transient response speed of the supply voltage and the load variety become faster; owing to adopting the piecewise linear slope compensation circuit, the disadvantages of current-mode control when the duty cycle is greater than 0.5, such as instability of open-loop, sub-harmonic oscillation, non-ideal loop response and an increased sensitivity to noise are eliminated; for adopting the phase-lock loop to the chip, the function of outer synchronization is realized, which is helpful to reduce the interference from other power supplies in the distributed power system, and the frequency capture ranges from 1.1MHz to 1.9MHz; since adopting pulse skipping mode, burst mode and outer synchronization, the operation mode can be chosen according to different applications, which makes full use of the chip's advantages. In addition, lots of protection circuits are integrated in the chip, such as over current protection, thermal shutdown, and so on.Furthermore, the thesis analyses the core factors that should be considered in layout design for analog IC. The layout of XD8183 is schemed out based on 0.6μm BiCMOS process, and it passes the post simulation. The results show that the switch efficiency is up to 96%; the quiescent current of this chip is only 10μA during operation, and drops below 1μA in shutdown mode; the work frequency is 1.5MHz unvaryingly. Because the main electrical characteristics can meet the specifications, the design project can be taped out. |
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