Routing of Analog Busses with Parasitic Symmetry

1. Routing of Analog Busses with Parasitic Symmetry Lars Schreiner, Markus Olbrich, Erich Barke, Volker Meyer zu Bexten

2. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

3. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

4. Motivation • Groups of wires (net bundles) have to be routed symmetrically • Symmetry = equal capacitive coupling and resistance for each wire • Automatic balancing of wire length • Automatic generation of shielding patterns • Automatic generation of slotted/split wires Lars Schreiner: ISPD 2005

5. Example of a Net Bundle with Parasitic Symmetry Lars Schreiner: ISPD 2005

6. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

7. Steps of Net Bundle Routing 1 Calculation of virtual terminals and net order Path search for net bundle Routing of the net bundle to the terminals Calculation of wire length differences and adjustment area search Use of Module generator for wire implementation 2 3 4 Lars Schreiner: ISPD 2005

8. Basic Procedure = Virtual Terminal T1a = Terminal T2a 1 2 3 4 T1b T2b Lars Schreiner: ISPD 2005

9. Separation of Terminal/Net Bundle Routing • Nets are treated and routed together as bundles. • Technology independent module generators can be used. • Problem complexity is reduced. • Keeping symmetry is easier. Lars Schreiner: ISPD 2005

10. 1 3 2 2 3 1 BUS-module from Module generator 3 2 1 virtual terminal terminal bundle Net Ordering During Path Search (1) • „False“ net order of the right terminal bundle • Consideration during path search necessary Lars Schreiner: ISPD 2005

11. 1 3 2 2 3 1 3 2 1 Net Ordering During Path Search (2) Possible solution of example Lars Schreiner: ISPD 2005

12. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

13. -45° 0° T- and L-Structures of Trapezoid Methodology = = Generator call: BUS N=3 LENGTH=4e-5 WIDTH=5e-6 LAYER=2 BEVELSTART=45 BEVELEND=0 Lars Schreiner: ISPD 2005

14. Benefits of Trapezoid Methodology • Universal use for many geometries • Lines, T- and L-structures are implemented by the same module generator • Technology information hidden in module generator • Router gets only necessary technology information • Shielding and Slotting are hidden in the generator • Easy maintainability and adaptation to new technologies Lars Schreiner: ISPD 2005

15. Adjustment Modules • Shorter wires have to be stretched • Two cases: • Adjustment to the favorable site • Adjustment to the unfavorable site Problem: Bent or terminal connection Solution: Adjustment modules Lars Schreiner: ISPD 2005

16. Examples of Adjustment Modules Lars Schreiner: ISPD 2005

17. Benefits of Adjustment Modules • Wire length balancing is done by module generator. • Different net bundle modules are generated for balancing bents, asymmetries, etc. • Resistive differences are adjusted. • Capacitive balancing is possible. Lars Schreiner: ISPD 2005

18. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

19. Hand Made vs. Router Lars Schreiner: ISPD 2005

20. Symmetric Coupling Consideration During Path Search Lars Schreiner: ISPD 2005

21. Contents • Motivation • Net Bundle Routing • Trapezoid Methodology • Results • Conclusions/Future Work Lars Schreiner: ISPD 2005

22. Conclusion • Routing of net bundles • Consideration of routing constraints • Parallel wires • Symmetric capacitive coupling • Wire length difference calculation • Symmetric terminal connection • Module generators • Trapezoid methodology • Adjustment modules Lars Schreiner: ISPD 2005

23. Future Work • 45° Routing • Twisted wires • Inductances Lars Schreiner: ISPD 2005