SNLS603D December 2020 – April 2025 DP83TG720R-Q1
PRODUCTION DATA
PCB traces are lossy and long traces can degrade signal quality. Traces must be kept short as possible. Unless mentioned otherwise, all signal traces must be 50Ω, single-ended impedance. Differential traces must be 50Ω single-ended and 100Ω differential. Impedance discontinuities cause reflections leading to emissions and signal integrity issues. Stubs must be avoided on all signal traces, especially differential signal pairs.
Figure 8-4 Differential Signal Trace RoutingWithin the differential pairs, trace lengths must be run parallel to each other and matched in length. Matched lengths minimize delay differences, avoiding an increase in common mode noise and emissions. Length matching is also important for MAC interface connections. All transmit signal traces must be length matched to each other and all receive signal traces must be length matched to each other.
Avoid crossover or vias on signal path traces. Vias present impedance discontinuities and be minimized when possible. Route trace pairs on the same layer. Avoid signals on different layers crossing each other without at least one return path plane between them. Differential pairs must always have a constant coupling distance between them. For convenience and efficiency, TI recommends routing critical signals first (that is, MDI differential pairs, reference clock, and MAC IF traces).