The native PWR-GND planes capacitor

This is the best solution to reduce the parasitic elements because the parasitic inductance is very small due to a very large contour and a good magnetic coupling factor. It can be modulated by a LC circuit if the largest dimension between the source and the load is less than 1 tenth of the minimum wave length (< 1/10 ∙ λ_min). Otherwise the PCB acts as a line or an antenna. The PCB capacitor consists in two copper planes with a dielectric inserted between the two planes. The equivalent capacitor (C_Pcb) is evaluated using the formula of the figure 6. For example, a 10cm x 10cm plane with 35µm thickness and separated by 1.6mm has a total inductance of 0.05nH and a capacitance equal to 271pF.

Fig. 6 A native PWR(VCC)-GND(VSS) planes capacitor

 

The frequency resonance of the plane is 1.4GHz. So, the power/ground plane techniques are efficient for high frequencies if the distance between the source and the load is short.