ADC08200: ADC output data

Part Number:ADC08200

Dear all,

I am using ADC08200 in one of my project. I am giving the input data with 1KHz pulse and I am giving the samples clock 20 MHz and tried with 50MHz also. i am getting ADC out constantly FF. The output of the ADC is not varying. Could you please give me the solution. Here i am attaching the schematic. R952 we are using provision to give clock from externally.

Thanks & Regards,

C Ashok Reddy