I have a question from a customer regarding the ADC Interface on Figure 60 of the datasheet. ". I am looking into driving a pair of ADCs with the ADL5505 (the ADCs may be the LT2107, LT2208 or an AD9268). Figure 60 in the data sheet shows a sample ADC interface. I may need a higher-order filter than that. The design is complicated a bit by the low output impedance of the ADL5505. I also don’t understand why C2A and C2B are grounded whereas C4 is differential. I would like to get some design guidance on this matter?"
Here is the figure: