Distorted o/p in EXC_OUT Signal from EVAL-AD2S1210SDZ

I am trying to use EVAL-AD2S1210SDZ to read the angle of a resolver. But when I checked the o/p Excitation signal in CRO, I am not getting a sine signal . I am getting a clamped distorted signal.

I am using the op-amp AD8397 with 0.866 gain. 

Can someone please help me to understand why not getting the exact signal at output.