In the evolution board schematics it is mentioned that the the input clock impedance is 66ohm(refer the attached figure).
But in data sheet it is mentioned 57Kohm. Can you explain the interface ?
The schematic is showing that the impedance seen from the clock balun is 66 ohms. This is due to the two 33 ohm resistors in parallel with the clock input of the AD9625. The input impedance seen across the clock input pins of the AD9625 is the high impedance (57Kohm) that you mention.
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