Where to Place Phase Delay Bumps on a Differential Pair

Where you put the phase delay bumps on a differential pair is not a preference. It changes your EMI, your common mode noise, and whether your signals arrive intact at the receiver. This video covers three constraints that work together to keep differential pairs clean: uncoupled length, which limits how long the two traces can separate before noise becomes a problem; static phase tolerance, which enforces length matching to prevent skew at the receiver; and dynamic phase delay, which controls how long the two signals are allowed to be out of phase at any point along the route. Phase bumps placed immediately after a mismatch starts suppress common mode voltage at the source. The same bump placed further down the trace after the mismatch has already propagated fixes almost nothing. The difference is demonstrated live in Allegro X and verified against a real Nvidia AGX Orin PCIe layer.