AD7682 datasheet(33/35 Pages) AD

33 / 35 page

Data Sheet

AD7682/AD7689

Rev. H | Page 33 of 35

APPLICATIONS INFORMATION

LAYOUT

The printed circuit board (PCB) that houses the AD7682/

AD7689 must be designed so that the analog and digital

sections are separated and confined to certain areas of the

board. The pin configuration of the AD7682/AD7689, 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

AD7682/AD7689 is used as a shield. Fast switching signals,

such as CNV or clocks, must not run near analog signal

paths. Avoid crossover of digital and analog signals.

Use at least one ground plane. It can be common or split

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

join the planes underneath the AD7682/AD7689.

The AD7682/AD7689 voltage reference input, REF, has a

dynamic input impedance and must be decoupled with minimal

parasitic inductances. This is achieved 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 of the AD7682/AD7689 (VDD and

VIO) must be decoupled with ceramic capacitors, typically

100 nF, placed close to the AD7682/AD7689, and connected

using short, wide traces to provide low impedance paths and to

reduce the effect of glitches on the power supply lines.

The AN-617 Application Note has information on PCB layout

and assembly. This information is particularly important for

guiding customers who do not have experience with WLCSP.

EVALUATING THE AD7682/AD7689 PERFORMANCE

Other recommended layouts for the AD7682/AD7689 are

outlined in the documentation of the evaluation board for the

AD7682/AD7689 (EVAL-AD7682EDZ/EVAL-AD7689EDZ).

The evaluation board package includes a fully assembled and

tested evaluation board, documentation, and software for

controlling the board from a PC via the converter and

evaluation development data capture board, EVAL-CED1Z.

AD7682 Datasheet(PDF) 33 Page - Analog Devices