Size and Performance Tradeoffs in Micro-Inductors for High Frequency DC-DC Conversion

This paper presents the design and measurement of optimized inductors-on-silicon (ldquomicro-inductorsrdquo) for use in high frequency DC-DC conversion applications. These ultra-compact low profile (< 70 mum) inductors range in area from 0.5-2.5 mm² . The design process utilizes optimization software that finds the optimal physical dimensions, to maximize inductor efficiency, given certain technology constraints. Optimized micro-inductors achieve measured inductance densities of 66 nH/mm² for a 2.5 mm² area, 110 nH/mm² for 1.3 mm² device and 82 nH/mm² for a 0.5 mm² footprint area. Measured saturation currents range from 0.15-0.5 A for the optimized devices.