AD5934_17 datasheet(30/31 Pages) AD | Impedance Converter, Network Analyzer

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AD5934

Data Sheet

Rev. E | Page 30 of 31

LAYOUT AND CONFIGURATION

POWER SUPPLY BYPASSING AND GROUNDING

When accuracy is important in a circuit, carefully consider

the power supply and ground return layout on the board. The

printed circuit board (PCB) containing the AD5934 should have

separate analog and digital sections, each having its own area of

the board. If the AD5934 is in a system where other devices

require an AGND-to-DGND connection, the connection should

be made at one point only. This ground point should be as close

as possible to the AD5934.

The power supply to the AD5934 should be bypassed with 10 µF

and 0.1 µF capacitors. The capacitors should be physically as

close as possible to the device, with the 0.1 µF capacitor ideally

right up against the device. The 10 µF capacitors are the tantalum

bead type. It is important that the 0.1 µF capacitor has low

effective series resistance (ESR) and effective series inductance

(ESI); common ceramic types of capacitors are suitable. The

0.1 µF capacitor provides a low impedance path to ground for

high frequencies caused by transient currents due to internal

logic switching.

The power supply line itself should have as large a trace as

possible to provide a low impedance path and reduce glitch

effects on the supply line. Clocks and other fast switching digital

signals should be shielded from other parts of the board by

digital ground. Avoid crossover of digital and analog signals

if possible. When traces cross on opposite sides of the board,

ensure that they run at right angles to each other to reduce feed-

through effects on the board. The best board layout technique

is the microstrip technique where the component side of the board

is dedicated to the ground plane only and the signal traces are

placed on the solder side. However, this is not always possible

with a 2-layer board.

AD5934 Datasheet(PDF) 30 Page - Analog Devices