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Micromachined inductors with submillimeter profiles and comparable electrical performance to thicker, commercially-available surface-mount devices, have been fabricated and characterized for low-megahertz dc-dc converters. The fabrication approach involves micron-scale lamination of Ni/Fe cores, combined with three-dimensional micromachined copper windings. The magnetic core of the fabricated inductor has 72 laminations of 1-μm-thick Ni/Fe films. The inductor dimension is 11.5 × 5.7 × 0.7 mm, and the dc resistance is 150 mΩ. A maximum Q of 9.2 at 3 MHz with an inductance value of 2.3 μH and a dc saturation current (I80) of 0.2 A were obtained. Use of this inductor in a regulated dc-dc boost converter circuit (7-12 V) operating at 2.2 MHz yielded 1.9-W power output at 71% efficiency.
Date of Publication: Sept. 2003