ADM 3251E: Preventing or minimizing EMI issues
The ADM3251 has Iso Power implemented - please see the Application Note AN-0971
From out of the note - specifc advice related to PCB design:
-Use a stack-up of at least four layers.
-Space the power and ground plane as closely as practical to optimize bypass.
-All vias in the power path should be as large as practical. Small vias have
high inductance and generate noise. Using multiple small vias is not as
effective in reducing via induct-ance as a single large via because the bulk of
the current goes through the closest via, even if multiple paths are present.
-Be very careful to route signal lines against a single refer-ence plane. It is
vital to maintain the image charge path so that image charges do not have to
travel by circuitous routes to meet back with the original signal on another
-Do not route high speed lines close to the edges of the PCB.
-Routing data or power off boards, especially through cables, can introduce an
additional radiation concern. Feedthrough filter capacitors or similar filter
structures can be used to minimize cable radiation.