I'm designing a board powered by a LiPo battery and the AP2114H LDO. At the battery side, I chose to use a 100nF ceramic and a 220uF tantalum. But I do not understand what are the considerations for choosing a low-ESR (and cheaper) tantalum vs. a high-ESR one. For example AVX TPS series vs. AVX TLN series.

Which tantalum capacitor would fit better, low-ESR (150 mOhms) or High-ESR (1300)?

The circuit itself is a wireless module, using the ESP8266.

  • \$\begingroup\$ Whatever the device calls for. \$\endgroup\$ Mar 5 '17 at 3:33
  • \$\begingroup\$ I specified which device is being used. Does that help decide which ESR to use? :/ \$\endgroup\$
    – Evgeny
    Mar 5 '17 at 3:35
  • \$\begingroup\$ Have you looked at the datasheet? \$\endgroup\$ Mar 5 '17 at 3:39
  • \$\begingroup\$ I'm sorry, but I don't understand. Which datasheet, of which component? The datasheet for the LDO does not specify anything useful about capacitors. \$\endgroup\$
    – Evgeny
    Mar 5 '17 at 3:40
  • \$\begingroup\$ Another BCD datasheet that fails to impress. \$\endgroup\$ Mar 5 '17 at 3:46

The tradeoff is that low ESR will generally provide better ripple / regulation (because it is lower impedance, so a given ripple current generates less ripple voltage), but regulators often have some requirement on ESR for stability -- basically their feedback network needs the damping from the output capacitor ESR to avoid oscillating. Extremely low ESR (like ceramic capacitors) also can lead to high Q resonances -- this can be a problem for the input capacitors since they battery/power leads can act both as an inductor and antenna.

Generally, regulator data sheets will specify the minimum capacitance and the required ESR range. In this case, the datasheet doesn't specifically list a requirement, but the at the top of the "electrical characteristics" table, the test conditions are listed as using 4.7 uF ceramic capacitors for input and output. So that is what I would use, rather than either of the tantalum choices.

Finally, it looks like the high ESR is a smaller package size for the same capacitance -- that may be a factor as well, even if it isn't relevant to you.

  • \$\begingroup\$ Thank you for the answer, really clarifies the thinking behind choosing a value here. And after digging in the datasheet, they insist that the capacitance should be 4.7uF. Even though I went the more traditional route of higher capacitance and a small ceramic. The 4.7uF can be even smaller (and cheaper). I don't know ... kinda lost here. \$\endgroup\$
    – Evgeny
    Mar 5 '17 at 3:54
  • 1
    \$\begingroup\$ They used a ceramic capacitor (lowest ESR) in the datasheet. Voltage regulators require low ESR capacitors. According to the datasheet, any Tantalum capacitor is okay. I think the voltage regulator is stable with both those capacitors, but the high ESR capacitor might add more noise to the output voltage. A larger capacitor (220µF instead of 4.7µF) for more noise reduction might not help. The ESR is more important. A large output capacitor could trigger the current limiter too much. I would select a 4.7µF low ESR at the input and output. \$\endgroup\$
    – Jot
    Mar 5 '17 at 4:35
  • \$\begingroup\$ Thanks, I didn't see that at first, but you are right, the data sheet specifies ceramic capacitors. \$\endgroup\$
    – Evan
    Mar 5 '17 at 5:09

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