Electronic – Decoupling capacitors


Many IC's I've seen suggest decoupling capacitors across Vdd to Vss – this is sensible.

However some IC's for example the dsPIC33FJ128GP802 has THREE Vss pins and only two Vdd pins (AVdd and Vdd.) So would I put a decoupling capacitor on each Vdd pin, or from each Vdd pin to each Vss pin?

Best Answer

I believe the general rule is 1 cap per Vdd pin.

Are you using a ground plane? If so, don't bother attaching the caps to Vss pins. However, if you are using a ground bus instead, then yeah you should attach the cathode of the caps directly to Vss.