In ref schematic for DAC AD9739 MIX MODE OUTPUTS are connected to secondary
of BALUN MABACT0039 while for normal mode it is connected to primary of baloon.
What is the difference?
The function of the balun here is to convert the differential signal to
single-ended signal. Per the spec of the balun, the primary side of the balun
is for singled ended signal and the secondary side of the balun is for
differntial signal. So the AD9739 differntial output is connected to the
secondary side of the balun to get the singled ended output from the primary