confusion on the power grounds. In your data sheet page 8, there is a note at
the bottom of the page which says that The AGND and DRGND should be tied
togather to a common ground plane. This means that we have to use only
"Analogue Supplies and Analogue grounds" or "Digital Power supplies and Digital
grounds" as with the suggested grounding configuration you can not mix two
power supplies, as one of them will not have any return ground.
What the datasheet recommends is to connect all the ground pins together to the
same ground plane. If your system has an Analog and digital ground plane then I
would recommend using only the Analog Supply and Analog Ground for the AD9430.
The terminology AGND, DRGND, AVDD, DRVDD refers to the circuits INSIDE the IC,
and not to whatever supplies and grounds you happen to have in your system.
There is a certain amount of inductance in the bond wires which connect the
silicon die to the pins. This means that we need to pin out the digital and
analog supplies and grounds separately, to avoid cross coupling of the
different parts of the chip via shared bond wire impedance. However, externally
all the grounds should be tied together to a low impedance ground plane and the
supply pins should be individually decoupled to this ground plane.