DS92CK16 Datasheet, PDF (10/11 Pages) National Semiconductor (TI) – 3V BLVDS 1 to 6 Clock Buffer/Bus Transceiver

Applications Information (Continued)
Termination:
Use a resistor which best matches the differential impedance
of your loaded transmission line. Remember that the current
mode outputs need the termination resistor to generate the
differential voltage. BLVDS will not work without resistor ter-
mination.
Surface mount 1% to 2% resistors are best.
Probing BLVDS Transmission Lines:
Always use high impedance (> 100kΩ), low capacitance
(< 2pF) scope probes with a wide bandwidth (1GHz) scope.
Improper probing will give deceiving results.
Cables and Connectors, General Comments:
Use controlled impedance media. The connectors you use
should have a matched differential impedance of about
Zo Ω. They should not introduce major impedance disconti-
nuities.
Balanced cables (e.g. twisted pair) are usually better than
unbalanced cables (ribbon cable, simple coax.) for noise re-
duction and signal quality. Balanced cables tend to generate
less EMI due to field canceling effects and also tend to pick
up electromagnetic radiation a common-mode (not differen-
tial mode) noise which is rejected by the receiver. For cable
distances < 0.5M, most cables can be made to work effec-
tively. For distances 0.5M ≤ d ≤ 10M, CAT 3 (category 3)
twisted pair cable works well, is readily available and rela-
tively inexpensive.
www.national.com
10