AD5933 datasheet(34/40 Pages) AD

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AD5933

Data Sheet

Rev. E | Page 34 of 40

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 containing the AD5933 should have

separate analog and digital sections, each having its own area

of the board. If the AD5933 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 AD5933.

The power supply to the AD5933 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

have 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

feedthrough 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 two-layer board.

AD5933 Datasheet(PDF) 34 Page - Analog Devices