I need a voltage regulator to drive an OLED display with 13V/ 50mAmp. I have 3.3 Volt to feed it with. I am thinking of using this boost regulator (because it is cheap): regulator

This regulator(AP3012KTR-G1) is an old boost regulator from 2010.
It says in the datasheet "L: SUMIDA CDTH3D14/HPNP-100NC or Equivalent" But this recommended inductor is not sold anymore. But according to the datasheet, it needs to be a 10uH anyway.

So I am looking at inductors at Digikey. Some values are really self-explanatory, but other ones I am not sure about:

1. "Inductance Frequency - Test" (in what way does this affect anything? important for boost regulator or not?)

2. "Frequency - Self Resonant" (in what way does this affect anything? important for boost regulator or not?)

3. "Q @ Freq" (in what way does this affect anything? important for boost regulator or not?)

4. "Material - Core" (any material that I should choose or avoid?)

5. "Type" (molded, multilayer thin film etc. is this important?)

inductor selection

So my question: can anyone help me understand in what way these five parameters affect when choosing an inductor?

This is for a product that I am developing btw.

  • \$\begingroup\$ Usually I just look at inductance, current rating and DC resistance. There are usually two limits to current. The saturation current limit and the thermal current limit. You have to make sure you RMS current does not exceed the thermal current limit, and you have to make sure your peak current does not exceed the saturation current limit (guard-band this... it can't go over at all). \$\endgroup\$
    – user57037
    Commented Oct 24, 2021 at 19:39

1 Answer 1


Quick Answer is use the SUMIDA CDRH3D14 upgrade, readily avail.

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  1. "Inductance Frequency - Test" for incoming quality testing. 100 kHz Typ.
  2. "Frequency - Self Resonant" If >> 10x switching rate then reduces self-capacitance load current, temperature rise of switch and phase of current may not be 90 deg when shutoff so current and voltage sensing is prudent with compensation as SRF is only >5x f sw. from parts avail.
  • However harmonics tend to be > 10x switching rate and some ZVS types fare better than others.
  1. "Q @ Freq" This correlates to DCR = X(f)/Q , higher Q is better for low loss but might make loop less stable.
  2. "Material - Core" Many type, you will learn have certain characteristics favourable to switchers for high mu, low loss, sharp saturation or soft but lossy depending on cost, quality and operating frequency. MgZn or NiZn plus ceramic binders.
  3. Type: Shielded, shape, yes is important to EMI, , losses, interference in layout, size matters, bigger often better, sometimes smaller is better depending on cost, and characteristics.
  • Shielded will have lower interference stray coupling and emissions , yet lower SRF !.

There are too many tradeoffs and scenarious to generalize, except avoiding saturation in high power at all costs might be prudent to add thermistor sensor on your 1st design as L turns from high impedance to just a short circuit with DCR when fully saturated.

L is rated at max current where L drops (typ. 10%) so on the edge of saturation. This datasheet is -35%. (65% of unloaded L)

  • 1
    \$\begingroup\$ oh wow. What that was a very quick answer! thank you! Thou I see that there seem not to be so much stock available for this part. So I think I will need to find an alternative anyway. So anyway I can get the "slow answer" also? =) \$\endgroup\$
    – mannen
    Commented Oct 24, 2021 at 18:45
  • \$\begingroup\$ 3k in stock digikey.com/en/products/detail/sumida-america-components-inc/… \$\endgroup\$ Commented Oct 24, 2021 at 18:54
  • \$\begingroup\$ yes, but I hope to sell a lot =) besides, I wonder about these parameters every time I need to choose an inductor... \$\endgroup\$
    – mannen
    Commented Oct 24, 2021 at 18:58

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