Wire Planning with consideration of Electromigration and Interference Avoidance in Analog Circuits
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Transcript of Wire Planning with consideration of Electromigration and Interference Avoidance in Analog Circuits
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
Outline
Introduction Preliminary Algorithms Experimental Result Conclusion and Future Work
Outline
Introduction Preliminary Algorithms Experimental Result Conclusion and Future Work
Introduction(1) Electromigration (abbreviated as EM) due to
insufficient wire width can cause the premature failure of a circuit. 1000mA
EM reduce the product circuit life
open
short
We must improve reliability
open
short[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.
These pictures are published in [11]
Introduction(2)
Circuit Simulation
Schematic
Partitioning+Floorplanning
Placement
Current-Driven Routing
Start
Current-Density Verification
EMViolations
Yes
No
Current-Density LayoutDecompaction
Electromigration-Robust Design
PhysicalDesign
1. Wire planning
2. Detail routing
Electromigration reduce circuit life
Total wiring area :840
Avoid electromigration to increase circuit life
Total wiring area :1830Electromigration aware
analog design flow
Avoid electromigration to increase circuit life
Total wiring area :2520
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.
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.
Outline
Introduction Preliminary
Terminology Problem Formulation
Algorithms Experimental Result Conclusion and Future Work
Terminology(1) - Adjust Line
If we can not find the feasible path by two pattern routing, the shorter line is applied.
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,
1
( , ) | | | |
(min ( , , , ))) ( , ,
i j i j
k
ilu lenlen
d
i
i j x x
j k
y
i j
y
k
( , , )llen i j k( , , )ulen i j k
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.
1S
6t
(1,6) 2c
(100,200)
(150,250) = (1,6) (1,6)
= 2 (|150 100 | | 250 200 |)
= 200
A c d
( , ) ( , )w i j c i j
, ,
A ( , ) ( , ) ( , ) ( , )i j i j
w i j d i j c i j d i j
( , )w i j ( , )c i j
Terminology(3) - Interference Predefined IP is regards as the obstacles To avoid the interference Space reserve the dead-space for obstacles
interfserious erence
wires in IP (obstacle)wires in chip
virtual obstacleoriginal obstacle
space reservation interferless ence
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).
Outline
Introduction Preliminary Algorithms
ILP-based Algorithm Graph-based Algorithm
Experimental Result Conclusion and Future Work
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 obstaclesOutput: 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;
Perform space reservation for obstacle
The user-defined space Construct a better wire planning with less
interference
dU
Initial circuits
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
(150,250)
(100,200)
(100,100)
(200,150) (250,150)
(200,50)
Construct the bipartite graph
1s
2s-5
-6
1S
2S
5
6
Construct the bipartite graph
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Calculate all source-to-target wirelengths
The wirelength of each source-target is computed The length is integrated into the ILP formulations.
d(1,3)=250;
d(1,4)=150;
d(1,5)=200;
d(1,6)=100;
d(2,3)=180;
d(2,4)=150;
d(2,5)=200;
d(2,6)=200;
ILP formulations
1
( , ) | | | |
(min ( , , , ))) ( , ,
i j i j
k
ilu lenlen
d
i
i j x x
j k
y
i j
y
k
1S
2S2S
1S
Determine the topology with proper wire width
Determine the topology with proper wire width by ILP formulations.
,
( , ) ( , )i j
Minimize A c i j d i j
1
( , ) m
ij
c i j O
1
( , ) n
ji
c i j I
Subject to
Kirchoff’s current law
Total wiring Area
Source driving current constraint
Target sinking current constraint
:
( , ) : Current from source to target
( , ) : Manhattan distance from source to target
: RMS Current values of source
i
j
where
c i j i j
d i j i j
O i
I : RMS Current values of target
: Coefficient between current value and the wire width
j
Wire width
1
,
( , ) ( , ), {1,2,..., }, {1,2,..., }i j
A c i j d i j i n j m
1 1
m n
j ij i
I O
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;
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;
ILP solver
ILP formulations
Result
Wiring area
wirelenth
Source driving current constraint
Target sinking current constraint
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.
Result
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;
1S
2S
6t
4t 5t
3t
32
2
3 1
1
Final EM-Oriented results
Wiring area is 1710
3 1001S
2S
6t
4t 5t
3t
2 200
2 180
3 150
1 200
Outline
Introduction Preliminary Algorithms
ILP-based Algorithm Graph-based Algorithm
Experimental Result Conclusion and Future Work
Algorithm
Input: (1) A set of sources and a set of targets (2) Their equivalent RMS current values (3) A set of obstaclesOutput: 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
Perform space reservation for obstacle
The user-defined space Construct a better wire planning with less
interference
dU
Initial circuits
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
(150,250)
(100,200)
(100,100)
(200,150) (250,150)
(200,50)
Construct the bipartite graph
1s
2s-5
-6
1S
2S
5
6
Construct the bipartite graph
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
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.
( , ) ( , )weight i j d i j
1S
6t
5
3(100,200)
(150,250)( , ) 1 (|150 100 | | 250 200 |)
100
weight i j
( , )d i j
Construct the bipartite graph
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1 0 01S
2S
6t
4t 5t
3t
5
6
3
3 3
2
(1,6) 1 100weight
Construct the bipartite graph
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1 0 0
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Sort the weights of all edges
The edge with smallest weight is first selected. 100(s1t6) The other weights are 150,150,150,200,200,200
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1 0 0
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
Remove the edge – iteration 1
The wire is built.
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
1 0 0
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Update weights of the relative edges – iteration 1
The current of source and target are updated.
1s
6t
5t
2s-2
-6
+0
+3
4t
3t
+3
+2
1 0 0
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Update weights of the relative edges- iteration 1
The selected edge is removed .
1s
6t
5t
2s-2
-6
+0
+3
4t
3t
+3
+2
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Remove the edge – iteration 2
The edge with small weight is selected.
1s
6t
5t
2s-2
-6
+0
+3
4t
3t
+3
+2
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Remove the edge – iteration 2
The wire is built.
1s
6t
5t
2s-2
-6
+0
+3
4t
3t
+3
+2
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Remove the edge – iteration 2
The current of source and target are updated.
1s
6t
5t
2s-0
-6
+0
+3
4t
3t
+1
+2
2 0 0
150
150
2 0 0
2 0 0
1 5 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Update weights of the relative edges– iteration 2
The selected edge is removed .
1s
6t
5t
2s-0
-6
+0
+3
4t
3t
+1
+2
2 0 0
150
150
2 0 0
2 0 0
2 5 0
1S
2S
6t
4t 5t
3t
5
6
3
3 3
2
Terminates until sources current are zero
The similar method is performed until the current of all sources have been assigned.
1s
6t
5t
2s-5
-6
+3
+3
4t
3t
+3
+2
100
150
200
150
150
1S
2S
6t
4t 5t
3t
3
2
1
2
3
Adjust the invalid edges
The invalid edge is adjusted by the push_line algorithm mentioned before.
1S
2S
6t
4t 5t
3t
EM-oriented (long lifetime)
Wiring are = 1830
Transform virtual obstacle into original one
The invalid edge is adjusted by the push_line algorithm mentioned before.
EM-oriented (long lifetime)
Wiring are = 1830
Less interference
1S
2S
6t
4t 5t
3t
Comparison of graph and ILP-based methods
Wiring area =1830
ILP-based method (Effective) Graph-based method (Efficient)
Wiring area = 1710
Outline
Introduction Problem Formulation Algorithms Experimental Result Conclusion and Future Work
Outline
Introduction Preliminary Algorithms Experimental Result Conclusion and Future Work
Experimental Result(cont’d) Platform
Name Specification
HardwareIBM Personal
ComputerPentium (R) D – 3GHz with
2GB RAM
OSMicrosoft
WindowsXPMicrosoft WindowsXP
Language C++ language Visual C++ 6.0
ILP Solver Lingo 11 Lingo 11
Experimental Result (cont’d)
( / ) 100ob ob chipR A A
: all area of obstacles
: chip areaob
chip
A
A
Circuit No. of obstacle
Rob (%) No. of source
No. of target
r1 10 8.2 3 7
r2 10 50.7 10 20
r3 10 21.7 16 34
r4 10 39.4 23 47
r5 10 29.2 33 67
r6 300 10.7 66 134
[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.
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.
Outline
Introduction Problem Formulation Algorithms Experimental Result Conclusion and Future Work
Conclusions and future work
First, the proposed ILP formulations determines the wire connections with the proper wire width by RMS current values of sources and targets . Our ILP-based method optimize wiring area without
obstacles.
Second, our method integrates the electromigration with obstacle for analog circuits to minimize the wiring area.
Third, the space reservation technique is used to avoid the interference between the wires and obstacles.
Compared to the results of greedy graph-based method, the proposed ILP-based method improved 13.24% wiring area on average.
Future work
The concept of signal integrity is considered to reduce the percentage of transformed edges[11].
How to obtain the better X-architecture results?
0tR 0.5tR
(a) signal loss (b) signal integrity
[11] J. Lienig, “Introduction to Electromigration-Aware Physical Design,” in Proc. of ACM International Symposium on Physical Design, pp.39-46, 2006.
Thank for your listening!