AD7982 datasheet(21/23 Pages) AD

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Preliminary Technical Data

AD7982

Rev PrC | Page 21 of 23

APPLICATION HINTS

LAYOUT

The printed circuit board that houses the AD7982 should be

designed so that the analog and digital sections are separated

and confined to certain areas of the board. The pinout of the

AD7982, with all its analog signals on the left side and all its

digital signals on the right side, eases this task.

Avoid running digital lines under the device because 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, should never run near analog signal paths. Crossover

of digital and analog signals should be avoided

At least one ground plane should be used. It could be common

or split between the digital and analog section. In the latter case,

the planes should be joined underneath the AD7982s.

The AD7982 voltage reference input REF has a dynamic, input

impedance and should be decoupled with minimal parasitic

inductances. This is done by placing the reference decoupling

ceramic capacitor close to, and ideally right up against, the REF

and GND pins and connected with wide, low impedance traces.

Finally, the power supplies VDD and VIO of the AD7982

should be decoupled with ceramic capacitors, typically 100 nF,

placed close to the AD7982 and connected using short and wide

traces to provide low impedance paths and reduce the effect of

glitches on the power supply lines.

An example of layout following these rules is shown in

Figure 28 and Figure 29.

EVALUATING THE AD7982’S PERFORMANCE

Other recommended layouts for the AD7982 are outlined

in the documentation of the evaluation board for the AD7982

(EVAL-AD7982-CB). The evaluation board package includes

a fully assembled and tested evaluation board, documentation,

and software for controlling the board from a PC via the

EVAL-CONTROL BRD3.

AD7982

Figure 28. Example of Layout of the AD7982 (Top Layer)

Figure 29. Example of Layout of the AD7982 (Bottom Layer)

AD7982 Datasheet(PDF) 21 Page - Analog Devices