Wireless power delivery between stacked chips makes system in a package (SiP) more compact and reconfigurable. However, to reduce the ripple of recovered voltage, a large on-chip filter capacitor is required, which is chip-area-inefficient. A multiphase power transmission approach is proposed to solve this problem. We implemented an inductive-coupling power delivery system with four power transmission channels. The clock of each channel has a μ/2 phase delay against the previous channel, and the outputs of all the channels are connected in parallel to a filter capacitor and a load. The measurement results show that the multiphase approach successfully reduced the ripple of the voltage from 200 mV at one channel to 15 mV at four channels. The test chip is fabricated using 0.18 μm standard complementary metal oxide semiconductor (CMOS) process.
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