Berkeley ELENG 290C - Lecture 2: High-Speed Link Overview and Environmen (15 pages)

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Lecture 2: High-Speed Link Overview and Environmen



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Lecture 2: High-Speed Link Overview and Environmen

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Lecture Notes


Pages:
15
School:
University of California, Berkeley
Course:
Eleng 290c - Advanced Topics in Electrical Engineering: Advanced Topics in Circuit Design

Unformatted text preview:

EE290C Spring 2011 Lecture 2 High Speed Link Overview and Environment Elad Alon Dept of EECS Most Basic Link Keep in mind that your goal is to receive the same bits that were sent EE290C Lecture 2 2 Why Wouldn t You Get What You Sent EE290C Lecture 2 3 Eye Diagrams V1 This is a 1 V0 tb This is a 0 Ve Eye Opening space between 1 and 0 te With Both With voltage noise With timing noise EE290C Lecture 2 4 BER clk BER Bit Error Rate Average of wrong received bits total transmitted bits Simplified example voltage only Vin ampl Voff BER 12 erfc 2 noise BER 10 12 Vin ampl Voff 7 n BER 10 20 Vin ampl Voff 9 25 n EE290C Lecture 2 5 What About That Wire Package On chip parasitic Line card trace Back plane trace termination resistance and device loading capacitance Back plane connector Line card via Kollipara DesignCon03 Backplane via EE290C Package via Lecture 2 6 Wire Models ICs usually use lumped models for wires Capacitance almost always matters Sometimes resistance Less often inductance Works because dimensions Let s look at some example and size numbers for links EE290C Lecture 2 7 Links and Lengths Chip to chip on a PCB Short and relatively well controlled Packaging usually limits speed Distance 3 6 Data rate 1 12Gb s Wavelength in free space Wavelength on PCB FR4 EE290C Lecture 2 8 Links and Lengths Cables connecting chips on two different PCBs Cables are lossy but relatively clean if coax Connector transitions usually the bad part Distance 0 5m up to 10 s of m Ethernet Data rate 1 10Gb s Wavelength in free space Wavelength on PCB FR4 EE290C Lecture 2 9 Links and Lengths High speed board to board connectors Daughtercard mezzanine type Backplane connectors Distance 8 up to 40 Data rate 5 20Gb s Wavelength in free space Wavelength on PCB FR4 EE290C Lecture 2 10 Transmission Lines Quick Review Delay Characteristic Impedance Reflections Loss EE290C Lecture 2 11 Reflections 2Z2 Z 1 Z2 Z2 Z 1 Z 1 Z2 Z1 1 Energy conserved 2 Voltages equal Z2 Sources of Reflections Z



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