Figure 4.21: Signal integrity produced by a unbalanced T topology.
Figure 4.22: Lattice diagram of an unbalanced T topology.
calculated with the use of a lattice diagram, although only a masochist would attempt to do
so instead of simulating it with a computer.
Figure 4.22
shows a lattice diagram that
calculates the first few reflections in
Figure 4.21
(the author must be a masochist). Referring
to the figure, vertical lines A and B represent the electrical pathway between the driver and
the junction, lines B and C represent the path between the junction and receiver 1, and lines
B and D represent the pathway between the junction and receiver 2. As more legs are added
to the topology, it becomes ever more sensitive to differences in the electrical length of the
legs. Furthermore, differences in the loading at each leg will cause similar instabilities.
So what can we learn from this? The answer is symmetry. Whenever a topology is
considered, the primary area of concern is symmetry. Make certain that the topology looks
symmetric from the point of view of any driving agent. This is usually accomplished by
ensuring that the length and the loading are identical for each leg of the topology. The
secondary concern in to try and ensure that the impedance discontinuities at the topology
junctions are minimized, although this may be impossible in some designs.
Chapter 5:
Connectors, Packages, and Vias
Summary :
Figure 4.21: Signal integrity produced by a unbalanced T topology. Referring to the figure, vertical lines A and B represent the electrical pathway between the driver and the junction, lines B and C represent the path between the junction and receiver 1, and lines B and D represent the pathway between the junction and receiver 2.
Tags :
topology,figure,between,represent,junction,diagram,lattice,lines,symmetry,differences,legs,concern,masochist