Design and Analysis of the DC-DC Converter with a Frequency Hopping Technique for EMI Reduction

As more circuit functions are integrated within a single die or small integrated package, the number of electromagnetic interference (EMI) problems caused by dc-dc converters is growing. In this paper, the dominant electromagnetic emission source on the dc-dc converter is identified by analyzing the power spectrum of the nodes. The noise scanner method is applied to a packaged single-chip prototype dc-dc converter. The results show that the dominant source of electromagnetic emission is the switching node of the converter, not the output node. The frequency hopping technique (FHT) is applied to the dc-dc converter to reduce the emission at the switching node, and its effectiveness is analyzed mathematically and experimentally. The mathematical model of FHTs is proposed to analyze its effectiveness in reducing EMI, and the optimal design using the FHT and dead-time control is fabricated with 0.18- μ m CMOS technology. The measured power spectrum reduction by using the optimal FHT design and dead-time control at the switching node is 16 dB. The EMI reduction amount of the proposed design measured by the IC-stripline method is 12.6 dB at the fundamental switching frequency.