EEVblog #1117 - PCB Power Plane Capacitance

[EEVblog]

Are power planes in a 4 layer PCB any good as a capacitor?
Can it work as one big bypass capacitor?
A look at an discussion on PCB layer stackups, and some measurements on 4 and 8 layer PCB power planes with different prepreg thicknesses and how well they work as a capacitor.

https://www.xilinx.com/support/documentation/application_notes/xapp623.pdf
https://www.researchgate.net/publication/242415439_High_Performance_FPGA_Bypass_Networks

[Bud]

Thanks, but I am unconvinced about the connection wires from the calibration plane to the board. Seemed good 20 cm of loop wire to me, which resonated with the inter-plane capacitance and that created a dip in the chart. Proper calibration has to be done at the connection points on the board.

[dardosordi]

Yeah, can we see the capacitors hooked up to the leads to compare ?

BTW, great video!

[PA0PBZ]

So it looks like the board is a low Q capacitor. Would be interesting to see what a similar board will look like when populated with the bypass capacitors or even fully populated.

[schratterulrich]

 I have written a tool to simulate the impedance of plane / cap combinations with irregular shapes. You can find it at leiterplatte.jimdo.com/pdn-sim/. Maybe it can be useful for someone.
You can see the effect of combining caps with interplane capacitance with this tool.