11.1.1 Microstrip vs. Stripline Topologies

As per the LVDS Application and Data Handbook (SLLD009), printed-circuit boards usually offer designers two transmission line options: Microstrip and stripline. Microstrips are traces on the outer layer of a PCB, as shown in Figure 24.

Figure 24. Microstrip Topology

On the other hand, striplines are traces between two ground planes. Striplines are less prone to emissions and susceptibility problems because the reference planes effectively shield the embedded traces. However, from the standpoint of high-speed transmission, juxtaposing two planes creates additional capacitance. TI recommends routing LVDS signals on microstrip transmission lines when possible. The PCB traces allow designers to specify the necessary tolerances for Z_O based on the overall noise budget and reflection allowances. Footnotes 1⁽²⁾, 2⁽³⁾, and 3⁽⁴⁾ provide formulas for Z_O and t_PD for differential and single-ended traces. ^(2)(3)(4)

Figure 25. Stripline Topology