Low-Resistance Integrated Toroidal Inductor for Power Management

Abstract

5.6 mm times 5.6 mm integrated toroidal inductors with reduced thickness down to 200 mum have been realized. A high inductance-to-dc resistance ratio have been achieved using a toroidal geometry. The realization features thick Cu winding and a thick laminated Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80 </sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> core with crossed anisotropy. Impedance measurements have been performed up to 100 MHz with dc bias current applied. As a typical result, we show an inductor with an inductance of 500 nH up to 10 MHz and a dc resistance of 95 mOmega. To the best of our knowledge, this is the highest inductance-to-dc-resistance ratio demonstrated by a fully integrated inductor. This demonstrates the interest of such integrated inductors to replace discrete components in compact low-power modules