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Step 6The Process: Inductor selection
The next step is to choose an inductor. This can be a bit of a pain, and there is a lot of math you can throw at the problem. However, the datasheet suggests (under "inductor selection") to get a 22uH inductor, with a ~1.2A saturation limit, and DC resistance of 0.02 ohms.
What we want is through-hole, which actually means its going to be hard to find an inductor; almost all inductors are surface mount. But I'll take a look at what digikey has to offer. I search for "fixed uH inductor ~smd ~smt" which means I don't want SMT/SMD (surface mount) and I want a non-adjustable inductor that is in the uH range (not mH or nH). I then filter out inductors with 1-3A current and 18-27uH inductance.
That filters it down to about a dozen choices. The SLF inductor is actually surface mount, and we're going to outright ignore the ones that cost more than $2.50. Inductors for small electronics like this should cost around $1-$2, as a guideline. That leaves us with the DN7418-ND "INDUCTOR 27UH POWER AXIAL" and the 6000-220K-RC "INDUCTOR HI CURRENT RADIAL 22UH." Both of these look good, with about ~1.5A saturation current and 0.07 ohm DC resistance.
I also check out Mouser. The online search for mouser isn't as nice as Digikey's so I end up looking at the paper catalog instead. I only found one inductor, really, the 18R223C (22uH radial power inductor) and/or the 18223C (axial version) that also has plenty of power capacity and a 0.03ohm DC resistance.
So, order 2 of each of these.
What we want is through-hole, which actually means its going to be hard to find an inductor; almost all inductors are surface mount. But I'll take a look at what digikey has to offer. I search for "fixed uH inductor ~smd ~smt" which means I don't want SMT/SMD (surface mount) and I want a non-adjustable inductor that is in the uH range (not mH or nH). I then filter out inductors with 1-3A current and 18-27uH inductance.
That filters it down to about a dozen choices. The SLF inductor is actually surface mount, and we're going to outright ignore the ones that cost more than $2.50. Inductors for small electronics like this should cost around $1-$2, as a guideline. That leaves us with the DN7418-ND "INDUCTOR 27UH POWER AXIAL" and the 6000-220K-RC "INDUCTOR HI CURRENT RADIAL 22UH." Both of these look good, with about ~1.5A saturation current and 0.07 ohm DC resistance.
I also check out Mouser. The online search for mouser isn't as nice as Digikey's so I end up looking at the paper catalog instead. I only found one inductor, really, the 18R223C (22uH radial power inductor) and/or the 18223C (axial version) that also has plenty of power capacity and a 0.03ohm DC resistance.
So, order 2 of each of these.
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