In automotive-used switching regulator applications, the characteristic of extreme conversion ratio (48V to 5V) and high switching frequency ($\mathrm{f}_{\mathrm{SW}}$) will give rise to considerable electromagnetic interference (EMI) issues, which is a tremendous obstacle to meeting CISPR 25 automotive standards. As shown in Fig. 8.11.1 (top), if $\mathrm{V}_{\text{Battery}}$ and $\mathrm{V}_{\mathrm{SW}}$ nodes are considered, the EMI problem can be divided into two areas. Region I is caused by $\mathrm{f}_{\mathrm{SW}}$ harmonic tones (