SLLSF54D October 2017 – March 2020 ISO7041
A minimum of four layers is required to accomplish a low EMI PCB design (see Figure 24). Layer stacking should be in the following order (top-to-bottom): high-speed signal layer, ground plane, power plane and low-frequency signal layer.
If an additional supply voltage plane or signal layer is needed, add a second power or ground plane system to the stack to keep it symmetrical. This makes the stack mechanically stable and prevents it from warping. Also the power and ground plane of each power system can be placed closer together, thus increasing the high-frequency bypass capacitance significantly.
Refer to the Digital Isolator Design Guide for detailed layout recommendations,.