Selecting a VRM Output Inductor

May 25, 2021 | Steve Sandler, Picotest

The selection of the output filter inductor is generally made using several figures of merit (FOM). Some of these figures of merit are discussed in the datasheet for a switching regulator application. Some are not. Often key data items are not present or poorly defined leading to uncertainty.

This article focuses on the impact of the inductor SRF on the switching regulator performance including how to model it, how to measure it, and why it matters. The impact on spike noise and EMI is discussed using several examples.

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