A differential pair is two closely coupled traces driven with complementary signals, so the receiver reads the difference between them and rejects noise common to both. USB, PCIe, Ethernet, LVDS and HDMI all use them. Designers keep both traces the same width and spacing, route them together on the same layer through the same vias, and match their lengths within a few mils so skew does not turn the signal into common-mode noise.
That PCIe differential pair has 30 mils of skew from the connector fanout, add a little serpentine on the short leg.
Also heard as
- diff pair
- pair
Related terms
Impedance control
Designing and building traces to a target impedance, such as 50 or 100 ohms, within a set tolerance.
Trombone
Back-and-forth trace meander added to lengthen a signal so its timing matches the others in its group.
Trace
Copper conductor path etched on a board layer, connecting pads, vias and planes.
Fanout
Short connections that bring each pin of a dense part out to a via so it can be routed on other layers.