The unused output should be connected to VCC through a 50Ω resistor. The datasheet is incorrect in Figure 4 on page 20. The OUT- terminal is shown connected to VCC with a 50kΩ resistor. The unused output must be connected to VCC with a 50Ω resistor to match the impedance of the driver. A 50kΩ resistor on the unused terminal can cause unwanted reflections on the coax data line.
Additionally, the Figure 4 shows incorrect 50kΩ value for the coax termination resistor--this too should be 50Ω to match the transmission line impedance. Only the line-fault resistor network should have values in kΩ.