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Crosstalk

Subject: Group Members

VLSI Shoaib Farooq

Instructor: (SP11-BEE-058)

Sir Atiq-ur-Rehman Sardar Amir

(SP11-BEE-00)

!"ai# $han

(SP11-BEE-0%0)

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CrosstalkTwo lines model of capacitive couplingCross sectional view of two adjacent

interconnect linesLumped-element coupling circuit model for 2

linesLumped-element coupling circuit model for 3

linesOverlap capacitancesDealing with Crosstalk

Presentation laout

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Whenever an interconnect is placed closed toany other interconnect line then the conductorsare coupled by parasitic capacitance.

Hence the pulsating voltage on one of the lineinduces a noisy signal on all the lines that arecoupled to it.

The noisy signal may introduce incorrect output.

Crosstalk

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Decreases the distance !"w two conductorsincreases in the parasitic capacitance and viceversa

#trongest coupling occurs if$

Coupling capacitance increases %oltage di&erence change ver 'uickl in time%L#( design deals with crosstalk ! reducing

coupling capacitance

Two lines model of capacitive coupling

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Consider the following )gure$

*rom a!ove )gure we can computed empiricale'uation for coupling capacitance per unitlength and also for total coupling capacitance

Cross sectional view of twoadjacent interconnect lines

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From previous gure and equations it is clearthat:

Using a small line spacing increases the couplingcapacitance

recaution: The lithography may be capable of producing

ner line spacing to avoid crosstal! in circuits.

Cross sectional view of twoadjacent interconnect lines+cont,.

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Phsical structure

/C e'uivalent model

0lternate model

Lumped-element coupling circuitmodel

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"ircuit model for #$line coupling problems

Lumped-element coupling circuitmodel for 3 lines

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"rosstal! also occur b%& overlapping lines ondi'erent material layers.

The critical parameter is the o(ide thic!ness b%&the t&o layers.

Try to minimi)e capacitances and ignoring

fringing elds.

For that purpose dra& interconnects on a givenlayer so that they are perpendicular to the line.Figure illustrated on ne(t slide

Overlap capacitances

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Overlap capacitances +cont,.

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*or estimating coupling parameters$ Computer programs use 1awells e'uation

of 41T to calculate 2D and 3D couplingparameters

4'uivalent /C model are simulated usingprogram ie #P(C4

Circuit designers 5 41 specialist$

Detailed eamination of crosstalk%L#( sstem designers$ #ee the result of these studies in various

parametric forms ie noise 6uctuation levels

on the nodes

Dealing with Crosstalk

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