AD5660 datasheet(18/20 Pages) AD

18 / 20 page

AD5660

Preliminary Technical Data

Rev. PrJ Page 18 of 20

POWER SUPPLY BYPASSING AND GROUNDING

When accuracy is important in a circuit it is helpful to carefully

consider the power supply and ground return layout on the

board. The printed circuit board containing the AD5660 should

have separate analog and digital sections, each having its own

area of the board. If the AD5660 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 AD5660.

The power supply to the AD5660 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), for example, common ceramic types of

capacitors. This 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 through 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.

AD5660 Datasheet(PDF) 18 Page - Analog Devices