I received a schematic with many inductors marked "600". These are small chip inductors for filtering spikes on audio and GPIO lines on a sound chip. The default value for the resistor is simply the Ohm. It would not make sense for the inductor to be 600 henries though. What value can I assume of these?

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  • \$\begingroup\$ What is their physical size, and approximated current-carrying ability? \$\endgroup\$
    – rdtsc
    May 4, 2016 at 4:51

1 Answer 1


Given the application, it is possible that these are meant to be ferrite beads (lossy inductors that turn high frequencies into heat while allowing low frequencies through unimpeded).

In that case, the "600" spec may mean 600 ohms at 100 MHz (100 MHz is the most common test frequency for ferrite beads that I've seen).

Here's an example: http://www.digikey.com/product-detail/en/wurth-electronics-inc/742792651/732-1593-2-ND/1638997

If you used a true inductor rather than a ferrite bead, I would guess that the LRC circuit formed by the inductor, the capacitance of the pin, and the resistance of the trace would be underdamped, resulting in overshoot and ringing. The overshoot and ringing would worsen your signal integrity, and the voltage overshoot could damage the pin.


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