White PaperSemiconductors & ICs

Decoupling Capacitor Selection for Modern PCB Design


Any digital part that has more than one operational state can benefit from a decoupling capacitor. In other words, all but the fastest switching digital parts can benefit from decoupling capacitors. The greater the switching current and the lower the switching time, the greater the importance of the decoupling capacitor in your circuit.

When the digital logic inside an integrated circuit, or when a digital output of an integrated circuit, changes state, the current demands of the IC change. The changing current requirements in inductors create a potential difference that separates the IC die’s Vcc and Gnd potential from the PCB’s Vcc and Gnd potentials. With shifted reference potentials, digital inputs may no longer be in defined logic levels. Decoupling capacitors placed close to the IC help to mitigate this issue as well as prevent noise from entering the power planes.

Designers can benefit from choosing the right decoupling capacitor early on in the design process. This whitepaper presents best practices for selecting decoupling capacitors for modern PCB design.

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