What are the key EMC requirements for high-speed differential cabling in edge boxes?

For high-speed differential cables in edge computing boxes, such as USB 3.0, PCIe, SATA, and HDMI, the quality of the cabling directly determines the EMC performance. Key requirements include:

1. Differential pairs must be of equal length and equidistant with a spacing error of <5mil to suppress common-mode components.

2. Impedance must be continuous and strictly controlled according to the chip datasheet's stack-up calculations, maintaining 100Ω ±10%.

3. Avoid crossing split reference planes; ensure the reference plane is intact and the adjacent layer is ground.

4. Ground planes on both sides of the differential cable; via spacing <λ/20 (e.g., 5GHz λ=60mm, λ/20=3mm, via spacing 3mm).

5. Connect common-mode suppression devices, such as CMZ2012A-900T, in series near the connector.

The CM common-mode and Z impedance 2012 are 2.0×1.2mm in size, and the 900T has an impedance of 90Ω. At 100MHz, it filters out high-frequency noise converted to common-mode. Meeting these requirements can reduce radiated emissions from high-speed interfaces in edge computing boxes by more than 10dB.