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In my vehicle Battery powered system which can vary from 12V to 36V , I want to use a Capacitor of minimum 10uF on the input. I have few doubts :-

  1. Which is best for 10uF value @ 36V - Ceramic/Tantulum/Electrolytic
  2. Can I use a 50V(Do I need to derate @ double the voltage) ceramic for 36V rating??
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Ceramics with class 2 dielectrics (X5R, X7R, Y5v and so forth) have a significant change of capacitance with DC bias, and for that reason I would normally use a device with a rated voltage of at least double the voltage I am bypassing with this technology.

When using Tantalum capacitors, manufacturers recommend derating devices with MnO2 electrolytes by 50% and to 80% of rated voltage for polymer electrolytes. Tantalums are popular as their CV product density is very high compared to other types.

Aluminium electrolytic capacitors are quite rugged and can be used closer to their rated voltage, but there is a trade-off, mainly in terms of ESR and physical size.

I do not know if your vehicle battery powered system is on the unswitched system in a vehicle (i.e. it is connected to a generator for charging); if so, you would need to withstand very large voltages during load dump

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There are many factors that help decide which kind of capacitor to use. None of those factors are revealed here. In reality, bypassing a large battery is not a particularly rigorous application and the type of capacitor is not of great concern.

A 50V (or 63V) capacitor would be quite reasonable for a battery with a nominal voltage up to 36V. That is probably what most designers would choose.

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Ceramics are good when you want really low ESR/ESL, Electrolytics when you want lots of bulk capacitance and Tantalums occupy some middle ground between the two. Just be aware, ceramics (well, X7R and X5R at least) lose much of their capacitance near their max voltage. A 50V 1uF ceramic might have 1uF at 10V but 0.2uF at 40V, Samsung and TDK have charts of this for a lot of their ceramics (many others don't). Electro's and Tantalums don't have this problem.

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