2.5 Inductor Selection

In the cases where there’s no metal shielding used in the EUT, the radiated emissions at the switching frequency harmonics are mainly radiated from the boost inductor. Inductor shielding can help mitigate the emissions in this frequency range. Shielded construction inductors should be used. And a type of molded inductors have better EMI performance compared with wirewound ones.

In this reference design with LP8866-Q1, an inductor with e-field shield is selected and maximum e-field reduction is realized when the shield is connected to ground. Experiments prove that the e-field shielded inductor can further improve the EMI performance. Comparisons of measurement results with different types of inductors are shown in Figure 16 and Figure 17. It can also be seen that the inductor selection impacts the whole frequency range till 300 MHz.