Is the AD9914's EPAD internally connected to AGND or DGND?
The AGND pins are connected to the EPAD internally.
If the EPAD is not externally connected to ground, the chip would still be
functional, however, the output performance of the device would be compromised
because of the noise. The reason being is that the purpose of the EPAD is for
thermal relief. Please refer to the tutorial MT-093 which is about Thermal
Design Basics for further information.