Active clamp circuits for switchmode regulators supplying microprocessor loads

Microprocessors such as the Intel Pentium Pro require over 10 amps of supply current at voltages in the range of 2-3.3 volts. The load demand can exhibit abrupt changes from light load (<0.5 amps) to full load in a matter of few hundred nanoseconds. Future processor generations are projected to require greater current (up to 60 amps) at supply voltages as low as 1 volt. Furthermore, these future processors are projected to impose load steps with di/dt on the order of 5 amp/nS when the processor switches between inactive and active modes, or vice versa. In this paper, we discuss some of the ramifications for the design of the power supply required to supply these microprocessor loads. We focus on the use of a paralleled active circuit which can be thought of as an active clamp which is designed to support the load during transients. Breadboards of these circuits have been built and tested. A prototype IC design is currently under test