I notice that my ADS5474 output data has a DC offset about +5mV, which is about 37 codes above the zero output code. For a continuous sine wave input, the output data swings around output code 8229, not 8192 (zero code), 8229 - 8192 = 37. The sampling clock frequency is 400MHz. The sine wave analog input is 300MHz.
At the ADS5474 analog input pins, there are the AC coupling capacitors; therefore, the ADS5474 analog input should not have any DC offset.
Is this +5mV DC offset level normal or abnormal? If it is abnormal, what is wrong with the DS5474 circuit? How do I fix it to bring the DC offset to normal?
Tuan To