Hello everyone, I am not good at electronic supplies (at least for now) so I am trying to look everyone's design then I will try to design mine. What I want to ask is here is a W5500 design. In this design they are probably use tantalum capacitor (C38 ,C37,C44,C46,C17) top of the left and bottom of the right. These 4 tantalum right ?
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When I look another design's Adafruit uses ceramic capacitors and Adafruit use 10uF instead of 22uF.(I don't have Adafruit's schematic but C22=C44 and C23=C17)
Here is my questions.
1-) Can I use ceramic capacitors even If schematic is polarized capacitor (tantalum or electrolyte) ?
2-) Can I use different sizes? For example they use 0402 but can I use 0805 ?
3-) One is using 22uF and the other one is using 10uF. Do different values prevent working ? (It should be but they are using different values.)
No, that picture shows 4 large MLCC ceramic caps (brown with metal end-caps), and a single tantalum cap (yellow-orange with a red at one end for polarity).
There's a round aluminium electrolytic at the top too and some smaller ceramic caps and a resistor (black with white printing).
I suspect they are decoupling caps which are usually not very critical in actual value, except that some need to be ceramic (low inductance).
Okay, thank you. Why are they huge? They can use 0603 like the rest and in their design, they drew with polarization but they are using ceramic, I don't understand
Capacitor size depends on the energy stored (proportional to capacitance and to voltage-squared). Different types have different energy storage densities, and electrolytics tend to be the highest energy density.
Electrolytics are polarized, so if the circuit is DC they can be used, but ceramic are non polarized and can always substitute for a DC capacitor.
The driving factors for SIZE are usually working voltage and capacitance. There will be little availability of a 10uF, 50V in size 603. I personally don't like anything smaller than 603 even for resistors when hand soldering prototypes. With Ceramic caps, you can always go with a higher voltage than expected. Not always true with Electrolytics or Tantalum.
Sometimes, its complicated, different types have different strengths and weaknesses and ESR, ESL, linearity, dielectric-absorption may all matter depending on the precise circuit - no simple answer I'm afraid.
For decoupling linearity and absorption are irrelevant though, so MLCC are fine, and often have the lowest ESL which does matter for logic chips with their ultra-fast switching.
To be precise some require the ESR to be within a range, not too large, not too small, to ensure loop-stablility. These are low-dropout regulators usually which have non-linear feedback loops.
If in doubt read the datasheet - always worth checking...
I believe this only happens if they are abused, which in practice means it does happen, and you have to be very careful to ensure over-voltage cannot happen in a circuit with a tant cap. Many organizations just avoid them because they have a catch-fire failure mode - these days large value MLCC caps are much more available and affordable anyway.
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