"The AD9229 has a stable and accurate reference voltage on chip,
which sets the full-scale voltage at the analog input channels."
this meas that the A/D chip include an accurate bandgap reference.
Generally the A/D converter chip have a PGA internally.
Never confuse the reference of the ADC with its input PGA -- they serve completely different purpose. The PGA can be done in several ways, you may not be able to find it at the input of the ADC since it can also be done digitally as long as the ADC has enough dynamic range.