lecture8_ee689_termination_txdriver

lecture8_ee689_termination_txdriver - ECEN689: Special...

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Sam Palermo ECEN689: Special Topics in High-Speed Links Circuits and Systems Spring 2011 Lecture 8: Termination & TX Driver Circuits
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Reading Will post some papers on voltage-mode drivers Termination Circuits TX Driver Circuits 2
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High-Speed Electrical Link System 3
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Termination Off-chip vs on-chip Series vs parallel DC vs AC Coupling Termination circuits 4
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Off-Chip vs On-Chip Termination 5 Package parasitics act as an unterminated stub which sends reflections back onto the line On-chip termination makes package inductance part of transmission line [ Dally ]
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Series vs Parallel Termination 6 Series Termination Parallel Termination Double Termination Low impedance voltage-mode driver typically employs series termination High impedance current-mode driver typically employs parallel termination Double termination yields best signal quality Done in majority of high performance serial links
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AC vs DC Coupled Termination 7 DC coupling allows for uncoded data RX common-mode set by transmitter signal level AC coupling allows for independent RX common-mode level Now channel has low frequency cut-off Data must be coded RX Common-Mode = IR/2 RX Common-Mode = V TT
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Passive Termination Choice of integrated resistors involves trade-offs in manufacturing steps, sheet resistance, parasitic capacitance, linearity, and ESD tolerance Integrated passive termination resistors are typically realized with unsalicided poly, diffusion, or n-well resistors Poly resistors are typically used due to linearity and tighter tolerances, but they typically vary +/-30% over process and temperature 8 Resistor Poly N-diffusion N-well Sheet R ( /sq) 90 ± 10 300 ± 50 450 ± 200 VC1(V -1 ) 0 10 -3 8x10 -3 Parasitic Cap 2-3fF/um 2 (min L poly) 0.9fF/um 2 (area), 0.04fF/um (perimeter) 0.2fF/um 2 (area), 0.7fF/um (perimeter) Resistor Options (90nm CMOS)
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This note was uploaded on 01/01/2012 for the course ECEN 689 taught by Professor Enjeti during the Spring '07 term at Texas A&M.

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lecture8_ee689_termination_txdriver - ECEN689: Special...

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