It has become clear to me, why the RLDOUT signal needs to be out of phase for Driven Right Leg.
The ADS1298ECGFE users guide describes in chapter 4.8.2. how to set the jumper J15 and J17 to get an in-phase or out-of-phase RLD signal. To get the in-phase RLD signal the jumper J17 must be set to 2-3, consequently RLDINV is connected to the TLV2221. Nevertheless the internal OpAmp 'RLD_AMP' and the external feedback (R8, C20) build an integrator what means that the input levels of the 'RLD_AMP' have to be the same. So is it not possible to use RLD_INV with the external feedback circuit?
Does it make any sense to use Driven Right Leg and the Shield Driver simultaneously? Or has it the effect of overcompensation?