Microfabricated coupled inductors for DC-DC converters for microprocessor power delivery

High-current, low-voltage power converters with fast transient response are needed for powering digital systems such as microprocessors. Microfabricated coupled inductors for such power converters are discussed. A four-phase microfabricated magnetic structure with 14 nH of inductance per phase has been fabricated for a 5 MHz, 5 V-to-1 V, 10 A dc-dc converter. The first prototype devices have been built with nickel-iron (NiFe) cores and copper conductors on a silicon substrate. Small-signal measurements on the inductors have been performed and predictions have been confirmed. A model for analyzing the performance of coupled inductors is presented. The devices have been implemented in a prototype converter and the measured performance is compared with the predicted results.