Design and optimization techniques of over-chip bond-wire microtransformers with LTCC core
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Accepted Version
Date
2017-09-13
Authors
Camarda, Antonio
Macrelli, Enrico
Paganelli, Rudi Paolo
Tartagni, Marco
Roy, Saibal
Romani, Aldo
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
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Abstract
This paper describes the realization of bond-wire micromagnetics by using standard bonding wires and a toroidal ferromagnetic low-temperature co-fired ceramic core with high resistivity. The proposed fabrication procedure is suitable for the development of magnetic components on the top of an integrated circuit with a small profile and a small size (<;15 mm 2 ). A transformer is designed and applied over chip, working in the MHz range with high inductance (~33 μH) and high effective turns ratio (~20). Applications include bootstrap circuits and micropower conversion for energy harvesting. Measurements demonstrate a maximum secondary Q-factor of 11.6 at 1.3 MHz, and a coupling coefficient of 0.65 with an effective turns ratio of 19, which are among the highest values reported for toroidal miniaturized magnetics. The achieved inductance density is 2 μH/mm 2 , along with an inductance per unit core volume of 15.6 μH/mm 3 , and a dc inductance-to-resistance ratio of 2.23 μH/Ω. The presented technique allows to obtain over-chip magnetics trough a postprocessing of the core, and it is also suitable for high-density power supply in package and power supply on-chip. Finally, a series of optimization techniques for planar core magnetic devices in order to maximize the inductance per unit area is discussed and applied to the considered case.
Description
Keywords
Energy harvesting applications , On-chip , Boost converter , Magnetic-core , Power , Inductors , Transformer , Silicon , Fabrication
Citation
Camarda, A., Macrelli, E., Paganelli, R. P., Tartagni, M., Roy, S. and Romani, A. (2018) 'Design and optimization techniques of over-chip bond-wire microtransformers with LTCC core', IEEE Journal of Emerging and Selected Topics in Power Electronics, 6(2), pp. 592-603. doi:10.1109/JESTPE.2017.2751745
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