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I am using the Analog Devices ADXL343 accelerometer (https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL343.pdf) which advises using a 1uF tantalium cap on one power line, and a 0.1uF ceramic on the other. I can't see any reason to prefer tantalium - ceramics of that size are easily available in my preferred 0402 chip size, and a fraction of the cost. Am I missing something? On Digikey tantalium cap one-off is about £1.50 but ceramic just 8 pence!

bgarrood
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  • from the datasheet (which you could have linked for a better question and to attract good answers), they suggest either 1 or 10µF. while small form factor of ceramic 1µF exist, im not so sure about 10µF. Also, the technology is only a suggestion. You have to think about desirable qualities for decoupling capacitors, and how tantalum and ceramic measure up against those expectations – Sclrx Jul 09 '20 at 07:05
  • Thank you! Link added. I have to admit I don't really understand how difference between the two will affect how the decoupling works. I have read a few things on the web but tends to talk about stability of capacitance with temperature/voltage which doesn't really affect me. Question probably is exactly that - how does tantalium vs ceramic affect desirable qualities for decoupling capacitors? – bgarrood Jul 09 '20 at 07:45
  • "Below 10 kHz the ESR of ceramic capacitors increases, so tantalum or aluminium electrolytic capacitors are recommended in this frequency range" That possibly explains tantalum for Vs. https://www.dataweek.co.za/news.aspx?pklnewsid=27008 – P2000 Jul 10 '20 at 06:34

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It should be fine.

The choice of decoupling capacitors is one of those matters that can either solved with "slap 0.1µF on that" or weeks of analysis.

what you want is a big reserve of charges to allow your chip to pull current without dropping the supply voltage, and a small but low ESR (equivalent serie resistance) cap to shunt the high frequencies that could come from it.

As a rule of thumb, 1µF + 0.1µF, both in ceramic, should be fine for the most common applications, including yours. I recommend reading up on the subject, it has helped me drastically as a designer. This answer and this application note are good starting points.

Sclrx
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