reference of AD9245

We use AD9245 to sample the signal detect single end amplifier with output voltage from 0 to 2 volts.  We connect this output to Vin+. My question is that should we connect the Vin- to ground or to a voltage reference of 1 volt. If we connect the Vin- to ground, the differential input of AD9245 will be from 0 to 2 volts. If we connect the Vin- to 1 volt reference,  the differential input of AD9245 will be from -1 to 1 volt.  Could you please tell us which solution is right or both are right?