1. The power plane should be close to the ground plane, coupled with the ground plane closely and arranged below the ground plane.
2. The signal layer should be next to the inner layer, not other signal layers.
3. Insulating digital circuit and analog circuit, if the conditions permit, make the analog signal line and digital signal line stratified layout with shielding.
4. High-frequency external interference is big, it is best to arrange it separately, using middle signal layer for transmission, in order to reduce external interference by inner layer of copper film.