AD5663

Rev. 0 | Page 20 of 24

BIPOLAR OPERATION USING THE AD5663

The AD5663 has been designed for single-supply operation,

but a bipolar output range is also possible using the circuit in

Figure 37. The circuit gives an output voltage range of ±5 V.

Rail-to-rail operation at the amplifier output is achievable using

an AD820 or an OP295 as the output amplifier.

The output voltage for any input code can be calculated as

⎥

⎦

⎤

⎢

⎣

⎡

⎟

⎠

⎞

⎜

⎝

⎛

×

−

⎟

⎠

⎞

⎜

⎝

⎛

+

×

⎟

⎠

⎞

⎜

⎝

⎛

×

=

R1

R2

V

R1

R2

R1

D

V

V

DD

DD

O

536

,

65

where D represents the input code in decimal (0 to 65,535).

V

5

536

,

65

10

−

⎟

⎠

⎞

⎜

⎝

⎛

×

=

D

This is an output voltage range of ±5 V, with 0x0000 corre-

sponding to a −5 V output, and 0xFFFF corresponding to a

+5 V output.

THREE-WIRE

SERIAL

INTERFACE

R2 = 10kΩ

+5V

–5V

AD820/

OP295

+5V

AD5663

R1 = 10kΩ

±5V

0.1µF

10µF

Figure 37. Bipolar Operation with the AD5663

USING THE AD5663 WITH

A GALVANICALLY ISOLATED INTERFACE

In process control applications in industrial environments, it

is often necessary to use a galvanically isolated interface to

protect and isolate the controlling circuitry from any hazardous

common-mode voltages that can occur in the area where the

DAC is functioning. iCoupler® provides isolation in excess of

2.5 kV. The AD5663 use a 3-wire serial logic interface, so the

ADuM1300 three-channel digital isolator provides the required

isolation (see Figure 38). The power supply to the part also

needs to be isolated, which 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 AD5663.

0.1µF

5V

REGULATOR

GND

DIN

SYNC

SCLK

POWER

10µF

SDI

SCLK

DATA

AD5663

ADuM1300

Figure 38. AD5663 with a Galvanically 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 AD5663 should

have separate analog and digital sections, each having its own

area of the board. If the AD5663 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 AD5663.

The power supply to the AD5663 should be bypassed with 10 μF

and 0.1 μF capacitors. The capacitors should be located as close

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

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

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

effective series resistance (ESR) and effective series inductance

(ESI) as in, 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 to 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.