EVAL-AD7982SDZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7982SDZ' PDF : 26 Pages View PDF
Data Sheet
APPLICATIONS INFORMATION
LAYOUT
The printed circuit board (PCB) that houses the AD7982 must
be designed so the analog and digital sections are separated and
confined to certain areas of the PCB. The pin configuration of
the AD7982, with its analog signals on the left side and its digital
signals on the right side, eases the task of separating the analog
and digital circuitry on a PCB.
Avoid running digital lines under the device; these couple noise
onto the die, unless a ground plane under the AD7982 is used
as a shield. Fast switching signals, such as CNV or clocks, must
not run near analog signal paths. Crossover of digital and
analog signals must be avoided.
It is recommended to use at least one ground plane. The
ground plane can be common or split between the digital and
analog sections. In the latter case, the planes must be joined
underneath the AD7982 devices.
The AD7982 voltage reference input REF has a dynamic input
impedance and must be decoupled with minimal parasitic
inductances. Decoupling is done by placing the reference
decoupling ceramic capacitor close to, ideally right up against,
the REF and GND pins and connecting them with wide, low
impedance traces.
Finally, decouple the power supplies of the AD7982, VDD and
VIO, with ceramic capacitors, typically 100 nF, placed close to
the AD7982 and connected using short, wide traces to provide
low impedance paths and to reduce the effect of glitches on the
power supply lines.
An example of layout following these rules is shown in Figure 40
and Figure 41.
AD7982
EVALUATING THE PERFORMANCE OF THE AD7982
Other recommended layouts for the AD7982 are outlined in the
UG-340 user guide for the EVAL-AD7982SDZ. The evaluation
board package includes a fully assembled and tested evaluation
board, the user guide, and software for controlling the
evaluation board from a PC via the EVAL-SDP-CB1Z.
AD7982
Figure 40. Example Layout of the AD7982 (Top Layer)
Figure 41. Example Layout of the AD7982 (Bottom Layer)
Rev. E | Page 25 of 26
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