Issue link: https://iconnect007.uberflip.com/i/1517668
100 PCB007 MAGAZINE I MARCH 2024 mission in only two wiring layers. Figure 1b shows the basic IMPS topology. e conventional metal wiring topology is to have signals on one metal layer and power and ground on separate metal layers. e resulting usage of these expensive metal layers is quite low. Signal layers may have only 50 to 60% utilization and power/ground layers only half that amount when either the coarse mesh or fine mesh is utilized (Figure 1c and 1d). ey may be made smaller (if signal losses can be tolerated), but the spacing cannot. High-speed, fast rise time signals are sensi- tive to crosstalk, so the signals still must be separated. IMPS uses that separation to route power and ground. To prevent current star- vation at devices, an adjacent metal layer running orthogonally is connected by bur- ied vias at each junction where the two lay- ers cross. is layer-pair topology is an "inter- connected mesh" that can thus provide all the power/ground connections without volt- age loss and connect the signal for these devices. Figure 2: Electrical performance of IMPS is very close to solid planes. Top: Power distribution explana- tion with the metal conductor's impedance vs. frequency using an HP8510 network analyzer with different capacitors in the layer-pair; Bottom: Power distribution impedance using the HP4291A impedance meter.