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Voltage Regulator De-coupling (Capacitor Voltages)

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David:
Hi all,
Just a quick question on de-coupling linear voltage regulators. How important is the voltage rating of the capacitor? I know it is good to "de-rate" the capacitor (e.g. use a 10V for 5V supply) but if you have say a 1.25V supply would using a 16V rated capacitor make any difference at all?

Dave

septer012:
I believe just from watching the video Dave did on capacitors, at least in electrolytics its the amount of pressure/strain the capacitor can be under before failing.  So I dont think a 100V capacitor would make any difference in a 5v application vs a 15v capacitor.

EEVblog:
For most applications the voltage rating is of little importance once you do the usual de-rating
If you want to go into ultra high reliability engineering (for something critical that must work for decades for example) then it's a different matter and would require thorough investigation. But that's a whole different ball game.

Dave.

GeekGirl:

--- Quote from: David on December 27, 2009, 11:46:38 pm ---Hi all,
Just a quick question on de-coupling linear voltage regulators. How important is the voltage rating of the capacitor? I know it is good to "de-rate" the capacitor (e.g. use a 10V for 5V supply) but if you have say a 1.25V supply would using a 16V rated capacitor make any difference at all?

Dave

--- End quote ---

Depends on if you are doing it for a one off or a mass produced product, one off, price does not matter, mass produced, every 1/2c matters, higher voltage rating is more expensive. I usually double the expected to voltage (to a point, (if I am expecting 340V then I might use a 450V)) ie if I need a 5V then I will choose a 10 or 16V.
 

Zero999:
I've found high temperature to be more damaging to electrolytic capacitors than voltage.

Using 105°C capacitors rather than 85°C capacitors is probably better reliability wise than higher voltage.

It depends on where the capacitor is and the power supply. If it's on the output of a linear regulator then there seems little point in de-rating it unless the output voltage is really close to the rated voltage. If its on the input to a linear regulator where the supply voltage can be unstable then it makes more sense to use a higher voltage.

If the capacitor is across the output of a 5V supply then 6.3V is probably fine but if it's a 6V supply then go for 10V.

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