I'm designing a board that contains an MCU and an 8 MHz crystal. I was planning on keeping the MCU power/ground localized and isolated from the main power supply power/ground except at a single point. I understand that for this scheme to work, the MCU decoupling capacitor must provide a low impedance path for high-frequency currents drawn from the MCU.
Does anyone know of any rules of thumb for acceptable frequency response for a capacitor used for this purpose? I'm using a 1uF ceramic through-hole (should probably use surface mount but I've got these things lying around) with the following frequency response:
I'm a little worried that it becomes inductive at only 2.5 MHz. Will this capacitor serve its intended purpose of decoupling an MCU run from an 8 MHz crystal?