1.Is it necessary for this configuration to
connect the SYNC-Pin?
2.Also, if SYNC is not used what should it be connected to?
1.With a single AD9253 there is no need to use the SYNC pin. It is
sufficient for the capture environment (such as an FPGA) to be configured to
capture the data relative to the DCO (output data clock) and FCO (output frame
2.SYNC is internally pulled to ground, so it can be left floating at the board
level when it is not being used.