AD7984BCPZ datasheet(23/24 Pages) AD

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AD7984

Rev. 0 | Page 23 of 24

APPLICATION HINTS

LAYOUT

The printed circuit board (PCB) that houses the AD7984

should be designed so that the analog and digital sections are

separated and confined to certain areas of the board. The

pinout of the AD7984, with its analog signals on the left side

and 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

AD7984 is used as a shield. Fast switching signals, such as CNV

or clocks, should not run near analog signal paths. Crossover of

digital and analog signals should be avoided.

At least one ground plane should be used. It can be common or

split between the digital and analog sections. In the latter case,

the planes should be joined underneath the AD7984.

The AD7984 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, ideally right up against, the REF and

GND pins and connecting them with wide, low impedance traces.

Finally, the power supplies VDD and VIO of the AD7984

should be decoupled with ceramic capacitors, typically 100 nF,

placed close to the AD7984 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.

EVALUATING THE AD7984 PERFORMANCE

Other recommended layouts for the AD7984 are outlined

in the documentation of the evaluation board for the AD7984

(EVAL-AD7984CBZ). 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 BRD3Z.

AD7984

Figure 40. Example Layout of the AD7984 (Top Layer)

Figure 41. Example Layout of the AD7984 (Bottom Layer)

AD7984BCPZ Datasheet(PDF) 23 Page - Analog Devices