On-chip coupled inductors with a novel spliced anisotropic and isotropic magnetic core for inductance and coupling enhancement. (February 2020) - He, Yuhan
Highlights: A novel design of 2D magnetic core to boost the coupling coefficient. Simultaneous high inductance gain, high inductance area density and high L/RDC . A high inductor efficiency of 96% for a 1.8 to 0.9 V DC-DC converter with a 152-mA phase current. Abstract: On-chip solenoid coupled inductors with a spliced anisotropic and isotropic magnetic core were proposed and demonstrated for high efficiency DC-DC conversion. The proposed magnetic core design avoids easy-axis excitation at the joint parts of the magnetic loop, which not only reduces the close-loop magnetic reluctance and therefore boosts the inductance value, but also reduces the magnetic flux leakage and therefore enhances the coupling factor (k). The fabricated inductors achieved a high inductance density of 127 nH/mm 2 and a large inductance to DC resistance ratio of 323 nH/Ω. The inductance gain is 51× compared to the air-core counterpart and 1.3× compared to the anisotropic-core counterpart. An enhanced k of 0.5 was also achieved compared to the k of 0.2 for the anisotropic-core counterpart. Consequently, the fabricated coupled inductors can achieve a high inductor efficiency of 96.0% for 1.8–0.9 V, 152 mA per phase, 170 MHz DC-DC conversion.