Summarizing Recommendations for Minimum Clearance
Here is a list of recommendations for ensuring minimum separation through air to meet typical hi-pot and cable ESD tests:
• Between PoE side and host side we need at least 40 mil (see bullets 3, 4, 5 in Fig. 10.5), but that may need to be increased to 50 mil (as per ECMA-287 too), depending on PCB-production tolerances and slightly higher actual-peak voltages than those assumed by Table 2K shown in Fig. 10.4.
• Staying completely within the PoE/MDI side, or completely within the host side, traces can actually run as close together as 5 mil from each other (same domain, see bullets 9, 10, and 11 in Fig. 10.5), but that may need to be increased to 8 mil based on PCB-production tolerances.