1
\$\begingroup\$

Can you help me identify the "L1" component in this schematic? It reads 33R@100MHz and is defined as an INDUCTOR. Maybe I'm reading it wrong (count on it), but I don't know how to deal with the @100MHz tag - resistors/inductors don't have a MHz as far as I know?

The closest I can get is a RC0603FR-0733RL (link: http://export.farnell.com/yageo-phycomp/rc0603fr-0733rl/resistor-rc22h-0603-33r/dp/9238301), but that's a resistor.

Line from EAGLE BOM: L1 33R@100MHz L-EUL2012C L2012C INDUCTOR, European symbol

Screenshot of schematic: EAGLE http://f.cl.ly/items/1v2w0r3s0G0i2H1l1g0r/Screen%20Shot%202015-08-11%20at%2020.19.12.png

Thanks a lot

\$\endgroup\$
7
  • \$\begingroup\$ It looks like an inductor with a reactance of 33R at 100 MHz. \$\endgroup\$ Commented Aug 11, 2015 at 18:27
  • 1
    \$\begingroup\$ ferrite bead, maybe? \$\endgroup\$
    – Nazar
    Commented Aug 11, 2015 at 18:32
  • 1
    \$\begingroup\$ Ferrite beads are frequently specified as a particular impedance at a given test frequency. \$\endgroup\$
    – Dave Tweed
    Commented Aug 11, 2015 at 18:32
  • 2
    \$\begingroup\$ To be fair: no need to chase the exact same part. Since it filters USB power line, you could wack in pretty much any inductor or ferrite (or even short it out) - for non-production purposes it'll do just fine. \$\endgroup\$
    – Ashton H.
    Commented Aug 11, 2015 at 18:34
  • \$\begingroup\$ Thank you all very much for helping out with this. I found an image of the component, not very good quality: cl.ly/image/3t3g1M3O0D18 - it reads R47, top left, right next to the USB connector. It might be a chinese substitute on this image. \$\endgroup\$
    – Benny Mose
    Commented Aug 11, 2015 at 18:35

2 Answers 2

2
\$\begingroup\$

What you see here, is not an exact specification of a component. It is more an indication to select a component.

It reads: The (complex) impedance of this inductor shall be 33 Ohms at 100 MHz. You have to select an appropriate inductor. Z = jωL is the formula to use.

You should take care of some more things. As this seems to be a power line for an USB port, the inductor should bear a continuous DC current of at least 500 mA without giving smoke signals. As many devices draw more than that, better go for 1 A. To keep losses low, the real part of the Impedance (i.e. ohmic resistance) must be below 100 mΩ I guess. This is called the series resistance in the data sheets.

\$\endgroup\$
0
0
\$\begingroup\$

This is not an inductor, rather it is a ferrite bead with a lossy (mostly resistive) insertion impedance of 33 ohms at 100MHz.

Probably like this 0805 (metric 2012) Taiyo Yuden BKP2125HS330-T part, rated at 4A and very cheap.

Ferrite beads often use the inductor symbol and are actually inductive at relatively low frequencies (say under 10MHz) but behave like a resistance at the 100MHz frequency where the impedance is specified, and behave like capacitors at very high frequencies. For DC they act as a very low resistance (< 20m\$\Omega\$ for the one mentioned above).

\$\endgroup\$
2
  • \$\begingroup\$ Interresting. I don't think Farnell carries this part; I'll try and look for an alternative. \$\endgroup\$
    – Benny Mose
    Commented Aug 11, 2015 at 21:00
  • \$\begingroup\$ I agree, that the behaviour of those devices is rather different for several frequency ranges. But there is no fundamental part called ferrite bead. So you should categorise it otherwise. As it consists a wire wound around something, I think the best classification is inductor. BTW the datasheet you are referring to calls it an inductor, too. Yes I know, everything below 1 GHz is DC :-) \$\endgroup\$
    – Ariser
    Commented Aug 14, 2015 at 10:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.