Component selections for the ETA3406 DC/DC converter

component-selectiondc/dc converterinductance

I was browsing Seeed Studio's Open Parts Library and found the ETA3406, which is a 1.5 MHz 1.2 A Step-Down Converter.

It's pretty cheap, and looks very useful for something I want to build, but the datasheet only shows it using a 2.2 µH inductor, which curiously is not in the Open Parts Library.

The datasheet also doesn't provide any guidance when it comes to selecting the inductor, all it says is:

If much smaller values are used, inductor current rises, and a larger
output capacitance may be required to suppress output ripple.
Larger values than LIDEAL can be used to obtain higher output current, but typically with larger inductor size.

I assume LIDEAL is that 2.2 µH value, but it's not very clear. Anyone have any tips on how to make the selection, given the scarcity of data?

Best Answer

If you zoom the datasheet, you can see that the diagrams actually recommends the use of a 2.2uH inductor!

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Although, it seems that Open Parts Library doesn't have these inductos either (but you can buy them cheap from Digikey, Mouser or any other distributor). To select one of them, is very important to take note on the maximum current the inductor can manage (as these ICs can have up to 1-2A as inductor current), so be careful!

This value is tipycal for step-down converters (I have used some of TI and other manufacturers and it's a standard value for a wide range of applications). I strongly believe you can use the datasheets of those parts to search for tips on value selection.