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Colotti J.Analog,RF and EMC considerations in printed wiring board design.pdf
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Destination Terminations

Driving waveform propagates at full intensity over trace

Reflections dampened

by terminating resistors(s)

Received voltage is equal to transmitting voltage (ignoring losses)

Increased peak current demands on driver

Delay = T

 

Zo=50

C

A B

50

1 A

0

1 B

0

1 C

0

0

T

2T

More applicable to daisy-chained receivers (first incident switching)

Thevenin termination reduces steady-state drive current

Revision 4

Copyright Telephonics 2002-2005

59

 

“Intentional” Mismatch Exampleple

Five selectable sources Four destinations Modeled signal paths

-CCA PWB

-Back Plane PWB

-Connectors

-Driver

Took advantage of relatively slow clock (30 MHz)

Revision 4

Copyright Telephonics 2002-2005

60

 

“Intentional” Mismatch Exampleple

Allow reflections to dissipate before clocking data (Clocks distributed point-to-point)

Revision 4

Copyright Telephonics 2002-2005

61

 

Power Distribution

&

Grounding

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