Hi,
We've not used any external components on the EVM for impedance matching other than the termination resistors R17/R18. The series caps C76/C77 are there for AC coupling, since the balun does not provide AC coupling as a transformer would, and the internal biasing resistors in the ADC would bias the signal to VCM if there is AC coupling in the system. The component in front labeled L7 is a zero ohm resistor - I do not know why it is labeled as L7 as we've not used those pads for anything.
Normally the termination resistors would be 25 + 25 ohm to match a 50 ohm input, but with these baluns our characterization engineer did use a network analyzer to sweep for the best termination. I find it interesting that the datasheet for the balun lists it as a '75 ohm balun' and the best termination was with 39 + 39 = 78 ohms. But we've not done anything onthe EVM to try to deal with the reactive elements of the ADC. Looking at the equivalent circuit inthe datasheet (Figure 31) for the analog input,the reactive parasitics are mostly the package bondwires and ESD protection circuitry so the input should be fairly well behaved. Since the Smith chart is in the User Guide for the EVM, I suspect the Smith chart was taken from the EVM and I don't know how much the EVM itself contributed to the overall result.
Regards,
Richard P.