I'd like to know if the ground pins are isolated between them. In addition I'd
like to know also if for every input/output corresponds an analogic ground.
The packaging of the AD8113 is designed to help keep the cross-talk to a
minimum. Each input is separated from each other input by an analog ground pin.
All of these AGNDs should be directly connected to the ground plane of the
circuit board.These ground pins provide shielding, low impedance return paths,
and physical separation for the inputs. All of these help to reduce cross-talk.
Each output is separated from its two neighboring outputs by an analog supply
pin of one polarity or the other. Each of these analog supply pins provides
power to the output stages of only the two nearest outputs. These supply pins
provide shielding, physical separation, and a low impedance supply for the
outputs. Individual bypassing of each of these supply pins with a 0.01 μF chip
capacitor directly to the ground plane minimizes high frequency output
cross-talk via the mechanism of sharing common impedances. Each output also has
an on-chip compensation capacitor that is individually tied to the nearby
analog ground pins AGND00 through AGND07. This technique reduces crosstalk by
preventing the currents that flow in these paths from sharing a commonimpedance
on the IC and in the package pins. These AGNDxxsignals should all be connected
directly to the ground plane.The input and output signals will have minimum
cross-talk if they are located between ground planes on layers above and below,
and separated by ground in between.
I would expect that the individual gnd pins are not connected internally in
order to prevent excess return current flowing in any one pin, and also to
provide isolation for the return currents, either way- these gnd pins must be
connected to a single gnd plane externally to avoid any potential difference
from developing between them.