please tell me What is AD9268‘s differential input resistance and differential input capacitance？I don’t find them in the datasheet。
Thanks for reaching out.
You can find the frequency response of AD9268 input at the S-parameter data located on its product page.
If you're designing the analog front-end of the ADC, you may want to refer to the Track mode measurement since the converter samples the input signal at this mode.
For more info on using the S-parameter data, kindly refer to this app note.