Decoupling ceramic capacitors on microcontroller rail.....voltage rating?

Hello,


I have a 3V3 rail which feeds a microcontroller and some opamps and comparators.

Each IC has a 100n, 16V, X7R ceramic capacitor near it for decoupling of noise.

Would it be OK if i change these to 50V rated X7R , 100n capacitors?


.....its just that there are already some 50V rated ones elsewhere in the schematic, and i would prefer to just use the same part throughout the schematic.

Yes if the size of the capacitor is not to large for the space available.

...So do you mean that the only difference between the 16V and 50V versions is the thickness?

...........Otherwise, i see no point in having a 16V range, since the 50V range costs the same and is just as good?

...or does the 16V range have lower ESL and lower ESR?

As far as i know ESR will depend upon temperature and frequency. It varies with package also.try to compare same family of caps from same mfg of same value and different voltages(Ex: 0.1uf,x7r,0402,10V Vs 0.1uf,x7r,0402,16V). I didn't find much ESR difference.

You may get low ESR & ESR value capacitor from low voltage capacitor or high voltage capacitor. Its upto the manufacturer specification. normally the ceramic capacitors have very low ESR & ESL compare to other tyeps. The operating frequency also very high. You can use upto the rated voltage. For example the tantalum capacitors must have to operate at 1/2 of the rated voltage.

Only different between 16v & 50v capacitor is size[cost also], but will not make big different for 0.1uF ceramic capacitors. For 3.3v operation you can use any of the voltage but it is recommended to use ceramic capacitors for decoupling. PP capacitors are even better but much expensive. The voltage indicates only the withstand capacity of the component & it will not make different in operation.

Regards
Udhay

..If the 50V, 100n, X7R capacitor is thicker then the 16V, 100n, X7R capacitor then surely it will have a lower ESR?

Higher voltage electrolytics have a higher ESR than lower voltage ones, but I don't know about ceramic capacitors which have very low ESR anyway. I don't think that any difference in ESR between the 16V and 50V capacitor is worth worrying about. I have been using the 50V type for years for decoupling and I have never experienced any problems in doing so. The reason for the 16V range is to save on space, weight and cost if ordering many thousands of them.

Well, bypass capacitors are used to decrease voltage ripple on the supply line. Actually it means that you have to select proper capacitors to provide known impedance at known frequencies. When someone just added 100nF caps, well, this value is not related to the design. So, you can use caps with any package. Just be sure that real voltage variation is below rated voltage. Good luck.

Usually lower voltage rated capacitors tend to have lower ESR.

However it would come down to the specific two capacitors in question to determine which has the lower ESR.

Though, I doubt that any difference in the ESR of the two decoupling capacitors is something to worry about.