As with most new high speed, high dynamic range ADCs, the analog input to the AD6644 is differential. Differential inputs allow much improvement in performance on-chip as signals are processed through the analog stages. Most of the improvement is a result of differential analog stages having high rejection of even order harmonics. There are also benefits at the PCB level. First, differential inputs have high common-mode rejection of stray signals such as ground and power noise. In addition, they provide good rejection of common-mode signals such as local oscillator feedthrough.