How to prevent crosstalk when multiple buses coexist in a smart controller PAC?

To prevent crosstalk when multiple buses (such as Ethernet, CAN, USB, and PCIe) coexist within a smart controller (PAC), frequency planning, physical isolation, and filtering are required. First, buses of different frequencies should be laid out separately; for example, high-speed buses (PCIe) and low-speed buses (CAN) should be arranged in separate zones, isolated by a ground plane. Second, each bus should be provided with an independent power supply and ground plane, and connected to the motherboard ground at a single point via a ferrite bead (such as PBZ1608A-102Z0T). Common-mode inductors (such as CMZ2012A-900T) should be used at bus interfaces to suppress common-mode noise, and ferrite beads should be connected in series on cross-zone signal lines.

During wiring, different bus signal lines should avoid parallel long-distance routing, and should cross perpendicularly when crossing. Clock signals should use spread spectrum technology to disperse energy. Tests show that this anti-crosstalk design can reduce inter-bus coupling attenuation by more than 40dB, and the system's bit error rate is less than 10^-8 when running at full load, meeting the IEC61000-4-6 conducted immunity test requirements.