The AD9680 can support DC coupling if the common mode voltage is kept at the recommended level. In DC-coupled applications, set the common-mode voltage to 2.05 V, ±100 mV to ensure proper ADC operation. The full-scale voltage setting must be at a 1.7 V p-p differential if running in a DC-coupled application.
ad4930. ad4930 need a common voltage but ad9680 cannot output a common voltage