What are the critical components in the AVdd filter circuits?
The critical components are the ones that are most effective close to the PLL frequency. The resistor and capacitors operate mainly at the lower frequencies, and serve to provide a stable supply at the lower frequencies. These components can not be eliminated, but their values can sometimes be modified if the resulting AVdd power is free of lower-frequency noise. It is usually not possible to eliminate the smaller capacitor. The ferrite bead works in conjunction with the internal capacitance of the AVdd input to eliminate high-frequency noise that could interfere with the operation of the PLL. The ferrite is not an optional component, although the exact value is not critical.
