The LO input is a high speed, fully differential analog input
that responds to differences in the input levels, not in the logic
levels. The LO inputs can be driven with a low common-mode
voltage amplifier, such as the National Semiconductor DS90C401
LVDS driver.
Figure 22 and Figure 23 show the range of common-mode voltages
and useable LO levels when the LO input is driven with a singleended
sine wave. Logic families, such as TTL or CMOS, are
unsuitable for direct coupling to the LO input.