AGND is the ground connection to internal analog circuitry
(ADCs, PGA, band gap reference, POR). To
ensure accuracy and noise cancellation, this pin must
be connected to the same ground as DGND, preferably
with a star connection. If an analog ground plane is
available, it is recommended that this device be tied to
this plane of the PCB. This plane should also reference
all other analog circuitry in the system.