Datasheet

April 14, 2008
Rev. 1.0 © 2008, National Semiconductor Corp.
5
The block diagram of Figure 2 details a clock distribution network in an ATCA backplane. The clock busses
have 130-ohm differential impedance and are doubly terminated with 80 ohms at either end of the backplane.
The parallel combination of 80-ohm resistors means that the MLVDS devices will be driving a 40-ohm load
termination. The maximum stub length from the backplane is defined in the ATCA standard as 1 inch or 2.54
cm.
Figure 3 shows a picture of a 14-slot ATCA backplane fully populated with DS91M040 evaluation boards.
Figure 3 - DS91M040 Evaluation Boards in an ATCA Backplane