# Is this capacitor suitable for boost converter (low ESR)?

I am about to build voltage booster (1.5V battery to 3.3V) with NCP1402.
Datasheet recommends 68μF tantalum or two 22μF capacitors for output. Schematic looks like this:

Output capacitor should have low ESR (page 16):

The output capacitor is used for sustaining the output voltage when the internal MOSFET is switched on and smoothing the ripple voltage. Low ESR capacitor should be used to reduce output ripple voltage. In general, a 47 μF to 68 μF low ESR (0.15 Ω to 0.30 Ω) Tantalum capacitor should be appropriate. For applications where space is a critical factor, two parallel 22 μF low profile SMD ceramic capacitors can be used.

I have smd ceramic 22μF caps, but I do not know whether they are suitable or not. I measured ESR of those caps with LCR meter:

8.30Ω @100Hz
0.63Ω @1kHz
0.04Ω @10kHz
0.04Ω @100kHz


ESR is fine for frequencies over 10kHz. But it is larger than recommended value at 1kHz and lower.

Is this capacitor suitable? Is it possible to ignore higher ESR at lower frequencies? Should I buy different/better caps?

• If stability is not mentioned, the converter will work but you will get more ripple with higher ESR. – Vladimir Cravero Feb 25 '17 at 18:20
• You can also lower the collective ESR by using more caps of a smaller value. – Los Frijoles Feb 25 '17 at 18:22
• Switch mode converters typically operate at high frequency to keep the magnetics small, and the one you linked to looks to run around 100 kHz, so the low frequency readings are pretty much meaningless for this application. I wouldn't really trust those readings either, I think that might be a limitation of your LCR meter measuring ESR of low value capacitors at low frequency. – Evan Feb 25 '17 at 18:52
• Yes, that convertor runs at around 100kHz. That's why I was hoping that I can ignore measurements at frequencies lower than 10kHz. – Chupacabras Feb 25 '17 at 21:06