The AD9680 has programmable input terminations. This termination can be programmed using SPI register 0x016. Available options are 400Ω, 200Ω, 100Ω or 50Ω differential.
The programmable input termination enables better filter integration and eases the filter design. For low frequencies, the input termination can be set to a high value. For higher input frequencies, an input termination of 100Ω or 50Ω differential is recommended.