I'm attempting to use the AD1853's DAC as a control signal, but I've noticed strange spurs at the output whenever I introduce a DC offset. For instance, if I excite the inputs with a positive DC offset of a few mV, then return to a 0mV 0Hz (0mV DC signal), then at the output of the DAC I see spurs at 20kHz, 40kHz, etc. on the frequency response.
If I increase the DC offset to 10mV, the spurs seems to start at 40kHz, and repeat at 40kHz intervals. If I decrease the DC offset to below 0mV, then I see spurs before 20kHz, and repeating at regular intervals.
Worse, these spurs modulate with my actual control signal whenever I add it to the input of the system, and I need the full 20kHz for my control signal.
Has anyone seen this? Is there any way to mitigate/remove these spurs? I know the AD1955 is recommended to replace the AD1853, but I cannot use either part if these spurs occur.