What is the proper termination for a BLVDS backplane?
A bus designer will determine the Bus LVDS termination resistor (RT) value by calculating the loaded impedance (ZL) of the bus. There are complex sets of variables that determine the ZL. The factors are the spacing between the loads, or plug-in cards, and the characteristic impedance (Zo) of the backplane trace. In addition, the loading from the plug-in card stubs, connectors, and transceiver loading also affect the ZL. For understanding purposes onlyand not an actual calculationassume a backplane with Zo =100Ω, 30 mm spacing between 20 slots, 30 mm stub lengths, 2 mm style connectors, and Nationals DS92LV010 Bus LVDS Transceiver on all cards. In this case, the ZL is about 54Ω.
