SNAA406B August   2024  – May 2025 LMK6C

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction and Test Methodology
  5. 2Simulation Setup
  6. 3Routing Topologies and Simulation Results
    1. 3.1 Single-Line
    2. 3.2 Star Line
    3. 3.3 Split Line
    4. 3.4 Star Line vs. Split Line
  7. 4Lab Measurements
    1. 4.1 Lab Measurement Setup
    2. 4.2 Lab Measurement Results and Correlation to Simulation Data
  8. 5Trace Length Mismatch Between Loads
  9. 6Application Example: FPD-Link
  10. 7Summary
  11. 8References
  12. 9Revision History

3.3 Split Line

The split line configuration can be used when loads are not co-located on a board. In this topology, the traces branch out close to the driver and behave as independent transmission lines for the majority of the trace distance.

Line resistors (Rt) are again added for impedance matching according to Equation 1.

Split Line Topology Figure 3-6 Split Line Topology
Split Line Simulation Results Figure 3-7 Split Line Simulation Results
Table 3-3 Split Line Rise or Fall Time
Number of Loads Trace Length - LM Rise Time (ns) Fall Time (ns)
2 2" 1.971 2.228
2 6" 3.762 4.556
4 3" 4.781 5.630
4 6" 7.998 10.16

For split line configurations, the number of loads and line length have a more drastic impact on signal integrity compared to the star line topology. As more loads are added an the trace length increases, the signal integrity worsens with more severe ringing and slower rise/fall times.