Power inductor in RF application

[radioLearner]

I purchased a 330 uH "power" inductor on eBay. The listing had the following data:

330UH Inductance 6.2x6x3.2mm Shield Surface Mount SMD Power Inductors
Product Name SMD Inductor
Type Surface Mounting(SMD )
Inductance 330uH (331 )
Body Size 6.2 x 6 x 3.2mm/ 0.24" x 0.24"x 0.12" (L*W*H)
Color Gray, Silver Tone
Material Ferrite Core, Metal
Weight 5g

The image for the part is at

I need a 330 uH inductor in an application where the maximum frequency is less than 700 kHz. Since there is no datasheet supplied with this part, and only the above listed data provided, I do not know if the self-resonant frequency of the part is appropriate for a 700 kHz application, i.e., that the self-resonant frequency of the part is higher than 700 kHz..

Since it is listed as a "power" inductor, is it automatically limited to "low" frequencies, perhaps less than 1 kHz, or is that not the case?

I tried determining the self-resonant frequency with a signal generator and oscilloscope putting the part in series with a 10 ohm resistor. As the frequency was increased the voltage across the 10 ohm resistor dropped, but kept dropping up to about 1.3 MHz, which seems too high to me for something listed as a "power" inductor.

I am new to RF work.

Thanks.

 

[FvM]

Did you review datasheets of similar inductors from major vendors? You'll notice SRF numbers in a 5 to 10 MHz range.

Switch mode power supplies are operated with up to several MHz these days, a 330 µH inductor would be used with at some 100 kHz´switching frequency.

 

[radioLearner]

Did you review datasheets of similar inductors from major vendors? You'll notice SRF numbers in a 5 to 10 MHz range.

Switch mode power supplies are operated with up to several MHz these days, a 330 µH inductor would be used with at some 100 kHz´switching frequency.

FvM,

Thanks for the reply. I did look at Panasonic and Coilcraft datasheets and never saw any indication of SRF for inductors listed for "power" use. They list maximal current which is what made me think that I was using the part inappropriately. Can you recommend a website where SRF is included in the power inductor specification?

Should I conclude from your reply and my attempt to measure the SRF as I described that the SRF could be in the 1.3 MHz range and that that would not be out of the question?

Is there anything in the specifications for the part which would give you pause for using it in the application I noted, i.e., in an application with frequencies of up to 700 kHz application?

 

[chuckey]

I suspect that the core losses might be high, so you can not build a high Q tuned circuit with it, but as a RF choke it would be OK.
Frank

 

[crutschow]

What is the inductor going to do in your circuit?

 

[radioLearner]

The inductor is used as part of a parallel resonance, band-pass filter.