Design and Optimization Techniques of Over-Chip Bond-Wire Microtransformers With LTCC Core

作者：Camarda Antonio^*; Macrelli Enrico^*; Paganelli Rudi Paolo; Tartagni Marco; Roy Saibal; Romani Aldo

来源：IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018, 6(2): 592-603.

DOI：10.1109/JESTPE.2017.2751745

• Bonding wire
• ferrite
• harvesting
• low-temperature co-fired ceramic (LTCC)
• magnetic transformer
• on-chip
• over chip
• power supply in package (PwrSiP)
• power supply on chip (PwrSoC)

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 (similar to 33 mu H) and high effective turns ratio (similar to 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 mu H/mm(2), along with an inductance per unit core volume of 15.6 mu H/mm(3), and a dc inductance-to-resistance ratio of 2.23 mu H/Omega. 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.

• 出版日期2018-6