When selecting a capacitor, consider the effects of DC bias voltage, tolerance, and temperature behavior. Ensure the capacitor maintains sufficient effective capacitance under all conditions. For decoupling, use multilayer ceramic capacitors (MLCC) with X5R or X7R dielectric.
A capacitor's inductance can increase the impedance at high frequencies. This occurs after the capacitor reaches its resonance frequency, typically above 1 MHz. As impedance rises, the capacitor's ability to filter high-frequency noise decreases. A higher capacitance value or larger physical size increase inductance. To improve noise filtering and decoupling across a wide range of frequencies, use a smaller capacitor in parallel with a larger one. This setup is effective especially on the buck input side where the highest current transients occur and is essential for RF noise-sensitive applications.