Post on 01-Jun-2018
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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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