Study of DC/DC converters in high-performance processor power delivery systems

With the advances in MOSFET technologies, switching a dc/dc converter at several MHz has become rather common. Also multiple phases of these converters are required in order to meet the increasing transient power requirements of the load. In this paper, the application of a multiple-phase, full synchronous dc/dc converter model when connected to a microprocessor power delivery system is addressed. Performance evaluation of the complete power delivery system based on a single and four-phase dc/dc converter is done. Advantages and disadvantages of each design are noted. Comparison is also made for various load representations. The load representations considered include a piecewise linear current source, a time-controlled switch, and a first and second-order polynomial voltage controlled current source. Differences in the output characteristics with a simple source replacement of the dc source and with an actual VRM are also highlighted.