Question: How should the resistor for series attenuation coupling in datasheet figure 4c be sized?
Answer: The attenuation resistor, R_ATTN, forms a voltage divider with the load presented by the MAX4002. Use the input impedance vs. frequency graph to determine the input impedance at the desired operating frequency, and size R_ATTN to create a voltage divider that will attenuate the maximum expected signal to within the input range of the MAX4002.