Wire Planning with consideration of Electromigration and Interference Avoidance in Analog Circuits

1. Wire Planning with consideration of Electromigration and Interference Avoidance in Analog Circuits 演講者: 黃信雄 龍華科技大學 電子工程系

2. Outline • Introduction • Preliminary • Algorithms • Experimental Result • Conclusion and Future Work

3. Outline • Introduction • Preliminary • Algorithms • Experimental Result • Conclusion and Future Work

4. Introduction(1) open short • Electromigration (abbreviated as EM) due to insufficient wire width can cause the premature failure of a circuit. 1000mA These pictures are published in [11] EM reduce the product circuit life We must improve reliability [11] J. Lienig and G. Jerke, “Current-Driven Wire Planning for Electrimigration Avoidance in Analog Circuits,” in Proc of Asia and South Pacific Design Automation Conference, pp. 783-788, 2003.

5. Introduction(2) Electromigration reduce circuit life Total wiring area :840 1. Wire planning 2. Detail routing Avoid electromigration to increase circuit life Total wiring area :2520 Avoid electromigration to increase circuit life Total wiring area :1830 Electromigration aware analog design flow

6. Introduction (3) • Previous Works • Minimize total wiring area without obstacle • Greedy-based approach [11] [19] • Minimize total wiring area with obstacle • Greedy-based approach [1][12] • Minimize total wiring area without interference consideration • Greedy-based approach [1] [11] [19][12] [11] J. Lienig and G. Jerke, “Current-Driven Wire Planning for Electrimigration Avoidance in Analog Circuits,” in Proc of Asia and South Pacific Design Automation Conference, pp. 783-788, 2003. [19] J.T. Yan Z.W. Chen and D.H. Hu, “Electromigration-Aware Rectilinear Steiner Tree Construction for Analog Circuits,” in Proc. of 18-th VLSI Design and CAD Symposium, CD-ROM, 2008. [1] T. Adler and E. Barke, “Single Step Current Driven Routing of Multiterminal Signal Nets for Analog Applications,” in Proc. of Design, Automation and Test in Europe, pp. 446-450, 2000. [12] J. Lienig, G. Jerke, T. Adler, “Electromigration Avoidance in Analog Circuits: Two Methodologies for Current-Driven Routing,” in Proc. of IEEE International Symposium on VLSI Design, pp. 372-37, 2002.

7. Introduction (4) • Contributions • First, to avoid the electormigration of the circuit, the greedy-based approach, which formulates the problem into the graph model, is used to automatically determine the feasible connections between sources and targets with the proper wire width. • Second, to avoid the interference between the obstacle and wires, the space reservation [5][11] is utilized for all obstacles. • Third, the proposed method efficiently determines the routing path to reduce the total wiring area.

8. Outline • Introduction • Preliminary • Terminology • Problem Formulation • Algorithms • Experimental Result • Conclusion and Future Work

9. Terminology(1) - Adjust Line • If we can not find the feasible path by two pattern routing, the shorter line is applied.

10. Terminology(1) - Adjust Line • The length from the source and target. is computed as follows [9], • where and are the additional wire lengths of the upper-L and low-L routing paths from source to target with the obstacle k,

11. Terminology(2) - Wiring area • To avoid the EM, the wire width is proportional to current value. We have the formula, where and are the wire width and current value for source i and target j, respectively. • Therefore, the wiring area is computed as, where is the constant.

12. Terminology(3) - Interference • Predefined IP is regards as the obstacles • To avoid the interference • Space reserve the dead-space for obstacles

13. Problem Formulation • Given: • A set of sources S = {s1 , s2 ,…, sn}with their corresponding root-mean-square (RMS) current values {O1 , O2 ,…, On}. • A set of targets T = {t1 , t2 ,…, tm}with their corresponding root-mean-square (RMS) current values {I1 , I2 ,…, Im}. • A set of rectangular obstacles B = { b1 , b2 ,…, bk}. • Objective: • To construct an wire planning result with minimal wiring area by consideration of the obstacles and electromigration (abbreviated as EM).

14. Outline • Introduction • Preliminary • Algorithms • ILP-based Algorithm • Graph-based Algorithm • Experimental Result • Conclusion and Future Work

15. ILP-based Algorithm(1) Input: (1) A set of sources and a set of targets (2) Their equivalent RMS current values (3) A set of obstacles Output: A EM-aware wire planning with minimal area Method: Step 1. Perform space reservation for obstacle; Step 2. Calculate the Length for Source-Target pairs; Step 3. Determine the Topology by ILP Formulations ; Step 4. Transform the M-architecture Results;

16. Perform space reservation for obstacle • The user-defined space • Construct a better wire planning with less interference

17. Initial circuits

18. Construct the bipartite graph

19. Construct the bipartite graph

20. Calculate all source-to-target wirelengths • The wirelength of each source-target is computed • The length is integrated into the ILP formulations. ILP formulations

21. Determine the topology with proper wire width Wire width • Determine the topology with proper wire width by ILP formulations. Total wiring Area Subject to Source drivingcurrent constraint Target sinking current constraint Kirchoff’s current law

22. Determine the topology with proper wire width min=wiring_area; wiring_area=c(1,4)*d(1,4)+c(1,5)*d(1,5)+c(1,6)*d(1,6)+c(1,7)*d(1,7)+ c(1,8)*d(1,8)+C(1,9)*d(1,9)+c(1,10)*d(1,10)+c(2,4)*d(2,4)+c(2,5)*d(2,5)+ c(2,6)*d(2,6)+c(2,7)*d(2,7)+c(2,8)*d(2,8)+c(2,9)*d(2,9)+c(2,10)*d(2,10)+ c(3,4)*d(3,4)+c(3,5)*d(3,5)+c(3,6)*d(3,6)+c(3,7)*d(3,7)+c(3,8)*d(3,8)+ c(3,9)*d(3,9)+C(3,10)*d(3,10); d(1,4)=18; d(1,4)=2070; d(1,5)=10850; d(1,6)=15190; d(1,7)=14570; d(1,8)=14190; d(1,9)=10200; d(1,10)=9330; d(2,4)=8850; d(2,5)=8270; d(2,6)=5950; d(2,7)=5450; d(2,8)=8850; d(2,9)=12780; d(2,10)=10290; d(3,4)=5030; d(3,5)=5430; d(3,6)=10390; d(3,7)=9770; d(3,8)=9070; d(3,9)=5700; c(1,4)+c(1,5)+c(1,6)+c(1,7)+c(1,8)+c(1,9)+c(1,10)=14; c(2,4)+c(2,5)+c(2,6)+c(2,7)+c(2,8)+c(2,9)+c(2,10)=32; c(3,4)+c(3,5)+c(3,6)+c(3,7)+c(3,8)+c(3,9)+c(3,10)=43; c(1,4)+c(2,4)+c(3,4)=10; c(1,5)+c(2,5)+c(3,5)=10; c(1,6)+c(2,6)+c(3,6)=9; c(1,7)+c(2,7)+c(3,7)=14; c(1,8)+c(2,8)+c(3,8)=16; c(1,9)+c(2,9)+c(3,9)=13; c(1,10)+c(2,10)+c(3,10)=17; Wiring area c(1,3) = 0; d(1,3)= 250 c(1,4) = 0; d(1,4)=150 c(1,5) = 3; d(1,5)= 100 c(1,6) = 2 ; d(1,6)= 200 c(2,3) = 2; d(2,3)= 180; c(2,4) = 3; d(2,4)= 50; c(2,5) = 0; d(2,5)=200; c(2,6) = 1; d(2,6)= 200; wirelenth ILP solver Source drivingcurrent constraint Target sinking current constraint Result ILP formulations

23. Determine the topology with proper wire width • After solving the ILP formulations , the connection is not exist if the current capacity is equal to zero. 1 c(1,3) = 0; d(1,3)= 250 c(1,4) = 0; d(1,4)=150 c(1,5) = 3; d(1,5)= 100 c(1,6) = 2 ; d(1,6)= 200 c(2,3) = 2; d(2,3)= 180; c(2,4) = 3; d(2,4)= 150; c(2,5) = 0; d(2,5)=200; c(2,6) = 1; d(2,6)= 200; 2 3 3 1 2 Result

24. Final EM-Oriented results • Wiring area is 1710

25. Outline • Introduction • Preliminary • Algorithms • ILP-based Algorithm • Graph-based Algorithm • Experimental Result • Conclusion and Future Work

26. Algorithm Input: (1) A set of sources and a set of targets (2) Their equivalent RMS current values (3) A set of obstacles Output: A EM-aware wire planning with minimal area Method: Step 1. Perform space reservation for obstacle; Step 2. Construct the bipartite graph; Step 3. Sort the weights of all edges; Step 4. Update weights of the relative edges; Step 5. Terminates until sources current are zero; Step 6. Adjust the invalid edges Step 7. Transform virtual obstacle into original one

27. Perform space reservation for obstacle • The user-defined space • Construct a better wire planning with less interference

28. Initial circuits

29. Construct the bipartite graph

30. Construct the bipartite graph

31. Construct the bipartite graph • To minimize total wiring area, the weights of all edges in the complete bipartite graph are assigned by the formula, where is the Manhattan distance for source i and target j. is a user-defined constant.

32. Construct the bipartite graph

33. Construct the bipartite graph

34. Sort the weights of all edges • The edge with smallest weight is first selected. • 100(s1t6) • The other weights are 150,150,150,200,200,200

35. Remove the edge – iteration 1 • The wire is built.

36. Update weights of the relative edges – iteration 1 • The current of source and target are updated.

37. Update weights of the relative edges- iteration 1 • The selected edge is removed .

38. Remove the edge – iteration 2 • The edge with small weight is selected.

39. Remove the edge – iteration 2 • The wire is built.

40. Remove the edge – iteration 2 • The current of source and target are updated.

41. Update weights of the relative edges– iteration 2 • The selected edge is removed .

42. Terminates until sources current are zero • The similar method is performed until the current of all sources have been assigned. 3 2 3 1 2

43. Adjust the invalid edges • The invalid edge is adjusted by the push_line algorithm mentioned before. EM-oriented (long lifetime) Wiring are = 1830

44. Transform virtual obstacle into original one • The invalid edge is adjusted by the push_line algorithm mentioned before. EM-oriented (long lifetime) Less interference Wiring are = 1830

45. Comparison of graph and ILP-based methods ILP-based method (Effective) Graph-based method (Efficient) Wiring area = 1710 Wiring area =1830

46. Outline • Introduction • Problem Formulation • Algorithms • Experimental Result • Conclusion and Future Work

47. Outline • Introduction • Preliminary • Algorithms • Experimental Result • Conclusion and Future Work

48. Experimental Result(cont’d) • Platform

49. Experimental Result (cont’d) [7] H.H. Huang, S.P. Chang, Y.C. Lin and T.M. Hsieh, “Timing-Driven X-Architecture Router among Rectangular Obstacles,” in Proc. of IEEE International Symposium on Circuits and Systems, pp. 1804-1807, 2008.

50. Experimental Result (cont’d) • Comparison of the wiring area of graph-based and ILP-based method, the additional wiring area is reduced by 13.24%. • The ILP-based method works efficiently.