Where in the signal chain do I actually have the 12 bit quantization? Is this at the ADC output or after some of the decimation/filtering?
The UG-570 doc stats the following:
The baseband Rx signal path is composed of two programmable analog low-pass filters, a 12-bit ADC, and four stages of digital decimating filters.
The ADC 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.