The Rx ADC used in AD936x devices is a highly oversampled sigma-delta modulator (SDM) with an output ranging from +4 to -4. A particular ADC output sample does not necessarily represent the input signal at a particular time. Rather, a positive value indicates that the input signal is more positive since the last sample and a negative value indicates that the input signal is more negative since the last sample. Note that since the ADC is highly oversampled, the ADC clock is much faster than the receive sample rate. Decimating and low pass filtering result in digital samples that represent the analog signal.
The ADC minimum and maximum operating output data rates are 25MHz and 640MHz respectively. The min and max rate need to be used as constraints for Rx digital data path design.