I have 8 boards connected to a backplane. At least four, but as many as
all 8 boards CAN be inserted at one time. Each board has a transceiver
connected to one bi-directional bus. Any of the transceivers can be the
driver. The transceiver nets to the connectors are about 3 inches long
and the backplane traces between connectors are about 1.25 inches. The
transceiver is a 74ACTQ245. All boards have a Z0 of about 60 ohms.
What termination techique should I try? I've tried using 10 or 20 ohm
series resistors near each transceiver, but the driver signal has a ring
back that crosses the 0.8 volt threshold on the falling edge. Because
any number of receivers can be on the bus at one time, I can't adjust
the termination resistance to accommodate all loading options.
Thank you in advance for your comments.
Cedar Rapids, IA
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