June 25, 2012
4:00 PM EST (1:00 PM PST)
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The integration of efficient power converters will enable improved performance-power-watt across the full spectrum of digital computing devices, from high-end servers to smart phones. Integrated Voltage Regulators (IVRs) can provide increased temporal and spatial resolution for dynamic supply voltage scaling, enabling improvements in energy efficiency by reducing the supply voltage during periods of low computational demand. IVRs offer further improvements in energy efficiency with reduced I2R losses in the power delivery network, and reduced power supply margins. Integration of the power inductor addresses this principle obstacle in achieving efficient, high current density switched inductor integrated power conversion. Planar spiral or other inductor topologies that can be constructed using the interconnects of a typical CMOS process are too resistive to provide efficient on-chip power conversion at reasonable current densities. This talk presents an integrated voltage regulator that uses custom fabricated thin-film magnetic power inductors. The inductors are fabricated on a silicon interposer and integrated with a multi-phase buck converter IC by 2.5-D chip stacking. Several inductor design variations have been fabricated and tested. The best performance has been achieved with a set of eight coupled inductors that each occupies 0.245 mm2 and provides 12.5 nH with 270 mW DC. With early inductor prototypes, the IVR efficiency for a 1.8V:1.0V conversion ratio peaks at 71% with FEOL current density of 10.8 A/mm2 and inductor current density of 1.53 A/mm2. At maximum load current, 69% conversion efficiency and 1.8V:1.2V conversion ratio the FEOL current density reaches 22.6 A/mm2 and inductor current density reaches 3.21 A/mm2.
Noah Sturcken is a graduate research assistant at Columbia University, currently pursuing his PhD. in electrical engineering in the Bioelectronic Systems Lab under the supervision of Kenneth Shepard. Noah holds a B.S. summa cum laude from Cornell University, and an M.S. from Columbia. His research interests include integrated voltage regulators and related technologies such as magnetic materials, and control systems. Noah recently interned at AMD’s Research and Development Lab.