How should differential signal wiring be standardized for a PAC (Power Controller Acoustic)?

The differential signal routing specifications for intelligent controllers (PACs) are crucial for ensuring signal integrity and reducing common-mode radiation. During routing, differential pairs (such as USB, HDMI, and Ethernet) should be strictly of equal length, with a length deviation of less than 5 mil, and the parallel spacing should be constant (usually twice the line width). Layer changes should be avoided as much as possible throughout the path. The reference plane must be complete, with a ground plane preferred over a power plane. Vias should not be inserted within differential pairs; if layer changes are necessary, return vias (at least two per pair) should be added near the change point. At connectors, differential pairs should be terminated as close as possible, and common-mode inductors (such as CMZ2012A-900T) should be used to suppress common-mode noise. Regarding impedance control, the differential impedance is typically 90Ω or 100Ω (depending on the protocol) and needs to be verified through simulation and TDR testing. After proper routing, the eye diagram opening of the differential signal can be improved by 30%, and common-mode radiation reduced by more than 20dB, meeting the IEC61000-4-6 conducted interference test requirements.