A 100MHz Eight-Phase Buck Converter Delivering 12A in 25mm2 Using Air-Core Inductors

We present a 100MHz eight-phase synchronous buck converter using air-core inductors. The voltage regulator (VR) chip was manufactured in a 90nm CMOS process and mounted on a flip-chip test package together with surface-mount inductors and decoupling capacitors. The measured peak efficiency is 84.0% for Vin/Vout= 2.4V/1.5V and 79.3% for 2.4V/1.2V. The VR delivers a load current of 12A in an area of only 25mm2 and 2.5mm height. This is the first demonstration of a high-frequency VR with air-core inductors, that reaches a record power density of 3.78kW/in3.