We need to perform a DC calibration of AD9652. We observed that, after a given time, the digital output code of AD9652 is suddenly altered even though a constant DC voltage is applied to the input of the device. Now, we realized that this is caused by the automatic background calibration of AD9652. When we switch off background calibration (by writing 0x1 to Register 0x4FB, Bit 0) we get a constant digital output code for a constant DC voltage.
This leaves us with some (ok, a bunch of ;-)) questions regarding the background calibration feature of AD9652:
1) Can you specify how the background calibration of AD9652 works?
2) What are the implications for device operation and performance, if the background calibration is permanently switched off?
3) Which performance metrics are affected by the background calibration (noise? offset? gain? linearity?) What do you mean by “slight degradation in performance” on page 26 of the datasheet?
4) Is there a way to manually set the background calibration “factors” by changing register settings?
5) Is there a way of tracking any alteration of the digital output code value due to background calibration?
6) When putting AD9652 to power-down and back to normal operation again (via register 0x08) a fast calibration is performed. Is this still true if the background calibration has been previously switched off via register 0x4FB?