AD5601 datasheet(17/20 Pages) AD

17 / 20 page

Preliminary Technical Data

AD5601/AD5611/AD5621

Rev. PrC | Page 17 of 20

USING AD5601/AD5611/AD5621 WITH AN OPTO-

ISOLATED INTERFACE

In process-control applications in industrial environments, it is

often necessary to use an opto-isolated interface to protect and

isolate the controlling circuitry from any hazardous common-

mode voltages that might occur in the area where the DAC is

functioning. Opto-isolators provide isolation in excess of 3 kV.

Because the AD5601/AD5611/AD5621 use a 3-wire serial logic

interface, they require only three opto-isolators to provide the

required isolation (see Figure 36). The power supply to the parts

also needs to be isolated. This is done by using a transformer.

On the DAC side of the transformer, a 5 V regulator provides

the 5 V supply required for the AD5601/AD5611/AD5621.

0.1

µF

10k

Ω

10k

Ω

10k

Ω

+5V

REGULATOR

VOUT

GND

DIN

SYNC

SCLK

POWER

µF

SYNC

SCLK

DATA

AD5601/

AD5611/

AD5621

Figure 36. AD5601/AD5611/AD5621 with an Opto-Isolated Interface

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 AD5601/

AD5611/AD5621 should have separate analog and digital

sections, each having its own area of the board. If the AD5601/

AD5611/AD5621 are 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 to the

AD5601/AD5611/AD5621 as possible.

The power supply to the AD5601/AD5611/AD5621 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), such as in 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.

AD5601 Datasheet(PDF) 17 Page - Analog Devices

AD5601 Datasheet(HTML) 17 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL