class19_Crosstalk_overview

# class19_Crosstalk_overview - C rosstalk Ove w and Mode rvie...

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Crosstalk Overview and Modes

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Crosstalk Overview 2 What is Crosstalk? Crosstalk Induced Noise Effect of crosstalk on transmission line parameters Crosstalk Trends Design Guidelines and Rules of Thumb Overview
Crosstalk Overview 3 Crosstalk Induced Noise Key Topics: Mutual Inductance and capacitance Coupled noise Circuit Model Transmission line matrices

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Crosstalk Overview 4 Crosstalk is the coupling of energy from one line to another via: Mutual capacitance (electric field) Mutual inductance (magnetic field) Mutual Inductance and Capacitance Mutual Inductance and Capacitance Zs Zo Zo Zo Mutual Capacitance , C m Mutual Inductance , L m Zs Zo Zo Zo C m L m near far near far
Crosstalk Overview 5 The circuit element that represents this transfer of energy are the following familiar equations Mutual Inductance and Capacitance Mutual Inductance and Capacitance “Mechanism of coupling” Mechanism of coupling” dt dI L V m Lm = dt dV C I m Cm = The mutual inductance will induce current on the victim line opposite of the driving current (Lenz’s Law) The mutual capacitance will pass current through the mutual capacitance that flows in both directions on the victim line

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Crosstalk Overview 6 The near and far end victim line currents sum to produce the near and the far end crosstalk noise Crosstalk Induced Noise Crosstalk Induced Noise “Coupled Currents” Coupled Currents” Zs Zo Zo Zo Zs Zo Zo Zo I Cm L m near far near far I Lm Lm Cm far Lm Cm near I I I I I I - = + =
Crosstalk Overview 7 Near end crosstalk is always positive Currents from Lm and Cm always add and flow into the node For PCB’s, the far end crosstalk is “usually” negative Current due to Lm larger than current due to Cm Note that far and crosstalk can be positive Crosstalk Induced Noise Crosstalk Induced Noise “Voltage Profile of Coupled Noise” Voltage Profile of Coupled Noise” Driven Line Un-driven Line “victim” Driver Zs Zo Zo Zo Near End Far End

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Crosstalk Overview 8 Graphical Explanation Graphical Explanation TD 2TD ~Tr ~Tr far end crosstalk Near end crosstalk Zo V Time = 2TD Zo Near end current terminated at T=2TD V Time = 0 Zo Near end crosstalk pulse at T=0 (I near ) Far end crosstalk pulse at T=0 (I far ) Zo Zo V Time= 1/2 TD Zo V Time= TD Zo Far end of current terminated at T=TD
Crosstalk Overview 9 Crosstalk Equations Crosstalk Equations Driven Line Un-driven Line “victim” Driver Zs Zo Zo Zo Near End Far End Driven Line Un-driven Line “victim” Driver Zs Zo Zo Near End Far End LC X TD = + = C C L L V A M M input 4 - - = C C L L T LC X V B M M r input 2 TD 2TD Tr ~Tr Tr A B TD 2TD Tr ~Tr ~Tr A B + = C C L L V A M M input 4 C B 2 1 = - - = C C L L T LC X V C M M r input C Terminated Victim Far End Open Victim

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Crosstalk Overview 10 Crosstalk Equations Crosstalk Equations Driven Line
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## This note was uploaded on 08/23/2009 for the course ECLT 762 taught by Professor Yinchaochen during the Spring '03 term at South Carolina.

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class19_Crosstalk_overview - C rosstalk Ove w and Mode rvie...

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