In fact, the more capacitance levels you choose, the flatter the impedance characteristics will be, but there is no need to use a lot of capacitance levels, the flatness of the impedance is of course good, but our ultimate goal is that the total impedance is less than the target impedance, as long as this requirement can be met Just do it.
The choice of which capacitance value in a certain level depends on the system clock frequency. As mentioned earlier, the parallel connection of capacitors has anti-resonance. When designing, care should be taken not to let the harmonics of the clock frequency fall near the anti-resonance frequency. For example, if you choose 0.47, 0.22, 0.1 or other values ​​on the fraction of a few microfarads, you need to calculate the following resonant frequency after installation.