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This letter demonstrates an on-silicon integrated thin film coupled inductor using a novel cascade matrix concept to suit multiphase integrated voltage regulator (IVR) applications. The novel cascade matrix coupled (CMC) stripline inductor facilitates all-phase-coupled configuration to reduce the phase ripple current in IVRs. It also shows excellent scalability and neat floor planning. Moreover, the proposed CMC inductor uses double layer metal scheme for windings and interconnects, which significantly reduces the ac winding resistance. A four-phase CMC inductor has been successfully fabricated on-silicon substrate and characterized, which uses conventional thin film magnetic core deposition process to achieve in-plane magnetic uniaxial anisotropy. The device occupies 3.2 × 1.7 mm2 floor area and provides 19.5 nH phase inductance with 120 mΩ dc resistance. The saturation current for each phase is up to 0.4 A when the phase inductance drops by approximately 20%. The coupling coefficient between any two phases of the proposed CMC inductor is 0.27, much higher and more controllable than that of toroid core-based coupled inductors. [ABSTRACT FROM AUTHOR]

Coupled inductors offer significant advantages over their uncoupled counterparts; however, with these advantages come a number of additional design caveats. The factors affecting the design and optimization of coupled stripline microinductors for PwrSoC applications are outlined, which include device area, the number of coupled phases, duty cycle, paralleling of coupled inductors, switching frequency, as well as thermal and saturation constraints. Results of this analysis are presented and discussed along with guidelines for the design of coupled stripline microinductors, which show that paralleling coupled inductors is the best route toward higher output current. Analytical models predict a peak inductor efficiency of 86.8% and 86.3% for fabricated 3 and 5-phase coupled stripline microinductors with an Ni45Fe55 core, respectively. Models are verified by measurements on prototype 3 and 5-phase converters with parallel coupled stripline microinductors over a range of operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, models that account for the duty cycle and phase shift angle of the applied phase voltages in coupled stripline microinductors are presented and are shown to have a significant impact on harmonic current amplitudes and therefore microinductor efficiency. The impact of a high coupling factor between two windings surrounded by a single core is also investigated. The models are validated using finite-element analysis and measurements. A three-phase-coupled microinductor has been fabricated with a Ni45Fe55 core and analyzed for a number of operating conditions. A prototype 1.6 W, three-phase converter utilizing this inductor has also been measured and is discussed in detail. The coupled microinductor is predicted to have a peak efficiency of 86.6% at 20 MHz in the prototype circuit. [ABSTRACT FROM AUTHOR]

Inductor-on-silicon research to date has focused on optimizing technologies for maximum power density and efficiency, with most design procedures based on computationally intensive methods. In this paper, a simple and intuitive method for designing microinductors based on a given dc–dc converter specification, which includes accurate models for all loss components, is presented. A detailed examination of variations in designs to realise the same circuit performance is presented. Finally, finite element analysis simulations demonstrating the accuracy of the models are given, along with measured results. [ABSTRACT FROM AUTHOR]

This paper details the design, fabrication, and characterization of silicon-integrated microtransformers for isolated bias supplies. Racetrack-shaped microtransformers were designed and fabricated using the advanced double-layer metal (DLM) microfabrication process. The DLM devices have high inductance density of more than 80 nH/mm2 with an efficiency of approximately 78.2% at 20 MHz at 0.5-W output. This is the highest efficiency and power density reported for an integrated transformer in the literature. The inductance drop is less than 20% with a bias current of 0.35 A with up to 6-kV dc breakdown voltage achieved. [ABSTRACT FROM AUTHOR]

Microfabricated inductors experience increasing interest and research activity because of their high potential in buck converters for power supply in package and power supply on chip applications. This paper details the modeling and optimization of microfabricated racetrack inductors. The analytical expressions derived characterize inductance, efficiency, and power density based on geometrical parameters, inductor current, and switching frequency. An accurate analysis of the inductor current that includes the impact of losses is performed to determine the switching frequency, the ac copper losses, and the core losses. The presented model is compared to finite element method simulations and reported results of three microfabricated inductors. Finally, the optimum tradeoff between efficiency and power density is identified using the Pareto front, which results from the evaluation of a large number of microfabricated inductors in the design space defined by the application. [ABSTRACT FROM AUTHOR]