AD5671R datasheet(30/32 Pages) AD

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AD5671R/AD5675R

Data Sheet

Rev. B | Page 30 of 32

APPLICATIONS INFORMATION

POWER SUPPLY RECOMMENDATIONS

The AD5671R/AD5675R is typically powered by the following

supplies: VDD = 3.3 V and VLOGIC = 1.8 V.

The ADP7118 can be used to power the VDD pin. The ADP160

can be used to power the VLOGIC pin. This setup is shown in

Figure 67. The ADP7118 can operate from input voltages up to

20 V. The ADP160 can operate from input voltages up to 5.5 V.

Figure 67. Low Noise Power Solution for the AD5671R/AD5675R

MICROPROCESSOR INTERFACING

Microprocessor interfacing to the AD5671R/AD5675R is done

via a serial bus that uses a standard protocol that is compatible

with DSP processors and microcontrollers. The communications

channel requires a 2-wire interface consisting of a clock signal

and a data signal.

AD5671R/AD5675R TO ADSP-BF531 INTERFACE

The I2C interface of the AD5671R/AD5675R is designed for

easy connection to industry-standard DSPs and microcontrollers.

Figure 68 shows the AD5671R/AD5675R connected to the Analog

Devices, Inc., Blackfin® processor. The Blackfin processor has

an integrated I2C port that can be connected directly to the I2C

pins of the AD5671R/AD5675R.

Figure 68. AD5671R/AD5675R to ADSP-BF531 Interface

LAYOUT GUIDELINES

In any circuit where accuracy is important, careful consideration

of the power supply and ground return layout helps to ensure

the rated performance. Design the printed circuit board (PCB) on

which the AD5671R/AD5675R are mounted so that the devices

lie on the analog plane.

The AD5671R/AD5675R must have ample supply bypassing of

10 µF in parallel with 0.1 µF on each supply, located as close to

the package as possible, ideally right up against the device. The

10 µF capacitors are tantalum bead type. The 0.1 µF capacitor

must have low effective series resistance (ESR) and low effective

series inductance (ESI), such as the common ceramic types,

which provide a low impedance path to ground at high

frequencies to handle transient currents due to internal logic

switching.

In systems where there are many devices on one board, it is

often useful to provide some heat sinking capability to allow

the power to dissipate easily.

The GND plane on the device can be increased (as shown in

Figure 69) to provide a natural heat sinking effect.

Figure 69. Pad Connection to Board

GALVANICALLY ISOLATED INTERFACE

In many process control applications, it is necessary to provide

an isolation barrier between the controller and the unit being

controlled to protect and isolate the controlling circuitry from

any hazardous common-mode voltages that may occur. iCoupler®

products from Analog Devices provide voltage isolation in excess

of 2.5 kV. The serial loading structure of the AD5671R/AD5675R

makes the devices ideal for isolated interfaces because the number

of interface lines is kept to a minimum. Figure 70 shows a

2-channel isolated interface to the AD5671R/AD5675R

using an ADuM1251. For further information, visit

www.analog.com/icoupler.

Figure 70. Isolated Interface

ADP160

LDO

ADP7118

LDO

INPUT

1.8V: VLOGIC

3.3V: VDD

ADSP-BF531

SCL

GPIO1

LDAC

PF9

RESET

PF8

SDA

GPIO2

AD5671R/

AD5675R

AD5671R/

AD5675R

GND

PLANE

BOARD

DECODE

SDA

CONTROLLER

ADuM12511

SCL

1ADDITIONAL PINS OMITTED FOR CLARITY.

ENCODE

SCL

SDA

ENCODE

DECODE

ENCODE

DECODE

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