A good explanation of Power Supply integrity

The resonator is formed between the power supply and the large plane of the formation. When the high-speed digital signal passes through, it is like a speedboat setting up a wave on the lake, and the voltage between the power supply and the ground fluctuates. Since it is a resonance (mechanical resonance), it requires a natural frequency, which is related to the shape of the power supply and ground plane, the medium parameters (dielectric constant, loss, thickness) in the middle. Once these parameters are set, the inherent frequency is fixed, just as the voice that a hacker can make is fixed. There are many inherent frequencies, just as the voice emitted by the hacker has many harmonic waves. For the PCB, the hammer that strikes it is a high-speed signal. High-speed signals are rich in spectrum components, some of which are the same as the inherent frequencies of PCB power sources, so they will fluctuate. If the minimum frequency is 10 GHz, and the signal spectrum component is no longer after 5 GHz, the signal cannot cause voltage fluctuations between power sources. The impedance analysis results in the relationship between impedance and frequency. Those peaks correspond to the inherent frequency, and the excitation of these frequencies will cause resonance. We take one of the mountain frequency and add a sine wave of the frequency for an AC analysis, we can observe the resonance mode (Voltage Distribution) on the ground plane of the power supply ). Pi design is to first perform impedance analysis to see where the lowest inherent frequency is. If it is too low, we need to change the structure (such as low power supply shape and medium thickness ), the minimum frequency is relatively high. Then, we compare several lower frequencies for AC simulation to see if there are any key devices in their corresponding voltage fluctuation modes that are most fluctuating. Then, we can apply the decoupling capacitor for AC analysis.