9.1 Application Information

The DS92LV040A is a Bus LVDS transceiver intended to be used in a differential backplane configuration. Transceivers or receivers are connected to the driver through a balanced media such as differential PCB traces. Typically, the characteristic differential impedance of the media (Z_O) is in the range of 50 Ω to 100 Ω. Two termination resistors of Z_O Ω each are placed at the ends of the transmission line backplane. The termination resistor converts the current sourced by the driver into a voltage that is detected by the receiver. The effects of mid-stream connector(s), cable stub(s), and other impedance discontinuity as well as ground shifting, noise margin limits, and total termination loading must be taken into account.

The output current is typically 12 mA. The current mode requires that a resistive termination be employed to terminate the signal and to complete the loop. Unterminated configurations are not allowed. The 12 mA loop current will develop a differential voltage of about 300 mV across a 27 Ω (double terminated 54Ω differential transmission backplane) effective resistance, which the receiver detects with a 230 mV minimum differential noise margin neglecting resistive line losses (driven signal minus receiver threshold (300 mV – 70 mV = 230 mV)). The signal is centered around +1.2 V (Driver Offset, V_OS ) with respect to ground. Note that the steady-state voltage (V_SS) peak-to-peak swing is twice the differential voltage (V_OD) and is typically 600 mV.