We want to use ADUM140E0BRZ for digital isolator and we study AN-1109 for layout suggest. It suggest to use 4 -layer PCB and a thin core layer is used for the power and ground planes as below picture, If we want to use 8-layer PCB , How to plan our PCB stack? Does ADI has suggestion to us for PCB stack? Does GND layer and power layer need tightly ? Second picture is our PCB stack now.