JAJSC32E September 2012 – June 2019 DP83848-EP
PRODUCTION DATA.
Place the 49.9-Ω,1% resistors, and 0.1-µF decoupling capacitor, near the PHYTER TD± and RD± pins and via directly to the Vdd plane. Stubs should be avoided on all signal traces, especially the differential signal pairs. See Figure 8-1. Within the pairs (for example, TD+ and TD–) the trace lengths should be run parallel to each other and matched in length. Matched lengths minimize delay differences, avoiding an increase in common mode noise and increased EMI. See Figure 8-1.
Ideally there should be no crossover or via on the signal paths. Vias present impedance discontinuities and should be minimized. Route an entire trace pair on a single layer if possible. PCB trace lengths should be kept as short as possible. Signal traces should not be run such that they cross a plane split. See Figure 8-2. A signal crossing a plane split may cause unpredictable return path currents and would likely impact signal quality as well, potentially creating EMI problems.
MDI signal traces should have 50 Ω to ground or 100-Ω differential controlled impedance. Many tools are available online to calculate this.