Coupling and Cross-talk Analysis in High Speed Interconnects

Md Amimul Ehsan

Electrical Engineering and Computer Science Department,

University of Kansas

December 01, 2015

Outlines Motivation Introduction Signal/Ground Via Near and Far end crosstalk Optimized and non-optimized S/G Via Conclusion

Motivation Due to technology miniaturization, crosstalk is

becoming increasingly becoming major concern in high speed designs.

Higher integration density, causes electromagnetic radiation in device space.

Merging process technology, mixed materials, system integration.

Coupling noise between the vias is a significant design consideration.

Objectives Study on coupling and crosstalk which is critical for

signal integrity.

Investigation of via physical dimensions on induced crosstalk.

Near end crosstalk (NEXT) and Far end crosstalk (EFXT) are analyzed for single ended and differential signal via.

Introduction

2D

Electromagnetic interference that disturbs neighbor is the crosstalk noise.

The time changing electric and magnetic field in signal conductor induce energy to propagate along victim conductor.

Fig. 1: Examples of crosstalk; two conductors sharing same ground [1]

Impacts of Via Dimensions Placement of signal and ground via.

Via radius.

Via pitch

Oxide insulator thickness (For TSV in 3D IC)

Signal/Ground Via Pattern

S1S2

S3 S4

G G G G

G

GGG

G

G

G

G

Fig. 2. Via arrangement 4 single ended signals with 12 grounds Fig. 3. Via arrangement 4 single ended

signals with 12 grounds (HFSS)

Single Ended Via Crosstalk

0 4 8 12 16 20-100

-84

-68

-52

-36

-20

Frequency (GHz)

NE

XT

(d

B)

d = 13 um

d = 18 um

Fig. 4. Near End Crosstalk of single ended signal Via with different pitch

0 4 8 12 16 20-100

-84

-68

-52

-36

-20

Frequency (GHz)

FE

XT

(dB

)

d = 13 um

d = 18 um

Fig. 5. Far End Crosstalk of single ended signal Via with different pitch

Differential Via Crosstalk

0 4 8 12 16 20-100

-84

-68

-52

-36

-20

Frequency (GHz)

NE

XT

(dB

)

Single Ended

Differential

Fig. 6. Near End Crosstalk of single ended and differential Via

0 4 8 12 16 20-100

-84

-68

-52

-36

-20

Frequency (GHz)

FE

XT

(dB

)

Single Ended

Differential

Fig. 7. Far End Crosstalk of single ended and differential Via

Optimized Differential S/G Via

Fig. 8. Differential signal assignment of non-optimized TSV

Fig. 9. Differential signal assignment of optimized TSV

Crosstalk Comparison

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.0 1.0

-0.001

0.000

0.001

0.002

-0.002

0.003

time, usec

V_N

EX

T

Readout

m1

Readout

m2m2

Time = 39.06 nsecV_NEXT = 0.003 Max

m1Time = 5.115 nsec

V_NEXT = - 0.001 Min

V_N

EX

T (

Vol

ts)

Time (µs)

Fig. 10. Step response simulation in near end crosstalk for non-optimized TSV pattern

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90.0 1.0

0.0000

0.0005

0.0010

0.0015

0.0020

-0.0005

0.0025

time, usec

V_N

EX

T

Readout

m1

Readout

m2 m2Time = 7.015 nsec

V_NEXT = 0.002 Max

m1Time = 86.17 nsec

V_NEXT = - 0.000 Min

Time (µs)

V_N

EX

T (

Vol

ts)

Fig. 11. Step response simulation in near end crosstalk for optimized TSV pattern

Conclusion This work investigated the via crosstalk noise under high

speed operations and discussed the impacts of various factors affecting crosstalk.

An analytical model can be proposed that could capture the induced coupling noise.

The coupling and crosstalk can be analyzed from the equivalent circuit of the differential pin pattern and can be applied for the design of crosstalk suppression.

References1. A. W. Barr, “Analyzing Crosstalk and Ground Bounce in Multiconductor Systems

Using SPICE Circuit Simulations,” AMP Journal of Technology, Vol. 3, Nov. 1993.

2. Yi, Y., Liu, Y., Zhou, Y., Becker, W.D. 2009. Minimizing crosstalk in high-speed differential buses by optimizing power/ground and signal assignment. In proc. of 18th IEEE Elect. Perform. Electron. Packag. Sys., Oct. 2009.

3. He, X., W. Wang, and Q. Cao, "Crosstalk modeling and analysis of Through-Silicon-Via connection in 3D integration," PIERS Proceedings, 857-861, Taipei, Mar. 25-28, 2013

4. Qian, L., Xia, Y., Liang, G. 2015. Study on crosstalk characteristic of carbon nanotube through silicon vias for three dimensional integration. Microelectronics Journal, 46, 7, (July 2015), 572–580.

5. Engin, A.E.; Narasimhan, S.R., "Modeling of Crosstalk in Through Silicon Vias," in Electromagnetic Compatibility, IEEE Transactions on , vol.55, no.1, pp.149-158, Feb. 2013

Thank you