Input EMI Filter Inductor

Question

Problem: Input EMI Filter Inductor. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

Switching converters and digital circuits on the board generate high-frequency noise that can travel back out through the 24V input power line. This conducted EMI (electromagnetic interference) can disturb other equipment connected to the same supply.

An LC filter at the input uses a series inductor and a shunt capacitor to ground. The inductor blocks high-frequency noise from passing through, while the capacitor shorts whatever noise gets past the inductor to ground. Together, they keep the power line clean.

Unlike a buck/boost inductor, this filter inductor carries only steady DC current (no large AC ripple), so the current and saturation margins are more relaxed.

Required: 10µH · ±20% · Irms ≥2A · Isat ≥2.5A · DCR ≤100mΩ · Shielded · SMD · −40°C to +125°C · RoHS

2. How to Find It on DigiKey

Go to DigiKey.com → Inductors, Coils, Chokes → Fixed Inductors

Apply these filters:

Inductance → 10µH
Current Rating (Amps) → 2A or higher
Current - Saturation (Isat) → 2.5A or higher
DC Resistance (DCR) → 100mΩ or lower
Shielding → Shielded
Type → Wirewound
Mounting Type → Surface Mount
Part Status → Active

Tip: A shielded inductor is important in EMI filter applications. An unshielded inductor would radiate the very noise you are trying to contain, defeating the purpose of the filter.

3. Key Specifications & What They Mean

Specification	Required	Why
Inductance	10µH	Blocks high-frequency conducted noise.
Tolerance	±20%	Standard for power inductors.
Current Rating (Irms)	≥2A	Board draws up to 1.5A; margin for heating.
Saturation Current	≥2.5A	Margin above 1.5A DC for transients.
DC Resistance (DCR)	≤100mΩ	Low loss; avoids voltage drop on input rail.
Type	Shielded Wirewound	Contains magnetic field; prevents radiated EMI.
Temp Range	−40°C to +125°C	Industrial operating conditions.
RoHS	Yes	Compliance required.

4. Selecting a Safe, Production-Ready Part

The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

5. Filtered DigiKey Link

➡ View Matching Parts — 10µH, Shielded, ≥2A, Isat ≥2.5A, DCR ≤100mΩ

20. Input EMI Filter Inductor