Ansys Employee
The answer depends on several things. Is this for a single IC and power supply or a network of ICs used with a power distribution network (PDN)? For a single device, you can use the rule of thumb which is to use a decoupling capacitor about ten times the value of the decoupling capacitance. For the latter, you will need to consider the impedance of PDN and the charge required by your ICs. You will need to know if this is for a digital or analog application as the calculation of capacitance either depends on the rise time of the signal or the operating frequency of the IC. In either case, more decoupling capacitance is preferred. To more accurately address this problem use of a simulation tool to address any parasitic resonances that occur due to the board layout is needed. The decoupling capacitor is usually placed near the power supply and ground and as close to the IC as possible.