AD5686 datasheet(22/24 Pages) AD

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AD5696/AD5694

Data Sheet

Rev. A | Page 22 of 24

APPLICATIONS INFORMATION

MICROPROCESSOR INTERFACING

Microprocessor interfacing to the AD5696/AD5694 is 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.

AD5696/AD5694 TO ADSP-BF531 INTERFACE

The I2C interface of the AD5696/AD5694 is designed for easy

connection to industry-standard DSPs and microcontrollers.

Figure 41 shows the AD5696/AD5694 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 AD5696/AD5694.

Figure 41. AD5696/AD5694 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. The PCB on which the AD5696/AD5694

are mounted should be designed so that the AD5696/AD5694

lie on the analog plane.

The AD5696/AD5694 should 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 capacitor is the tantalum bead type. The 0.1 µF capacitor

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

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

capacitors provide a low impedance path to ground at high

frequencies to handle transient currents due to internal logic

switching.

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

useful to provide some heat sinking capability to allow the

power to dissipate easily.

The AD5696/AD5694 LFCSP models have an exposed pad

beneath the device. Connect this pad to the GND supply for

the part. For optimum performance, use special considerations

to design the motherboard and to mount the package.

For enhanced thermal, electrical, and board level performance,

solder the exposed pad on the bottom of the LFCSP package to

the corresponding thermal land paddle on the PCB. Design

thermal vias into the PCB land paddle area to further improve

heat dissipation.

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

Figure 42) to provide a natural heat sinking effect.

Figure 42. Paddle 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.

The Analog Devices iCoupler® products provide voltage iso-

lation in excess of 2.5 kV. The serial loading structure of the

AD5696/AD5694 makes the part ideal for isolated interfaces

because the number of interface lines is kept to a minimum.

Figure 43 shows a 4-channel isolated interface to the AD5696/

AD5694 using the ADuM1400. For more information, visit

http://www.analog.com/icouplers.

Figure 43. Isolated Interface

ADSP-BF531

SCL

GPIO1

SDA

GPIO2

LDAC

PF9

RESET

PF8

AD5696/

AD5694

AD5696/

AD5694

GND

PLANE

BOARD

ENCODE

SERIAL

CLOCK IN

CONTROLLER

ADuM1400

SERIAL

DATA OUT

RESET OUT

LOAD DAC

OUT

DECODE

SCL

SDA

RESET

LDAC

VIA

VOA

ENCODE

DECODE

VIB

VOB

ENCODE

DECODE

VIC

VOC

ENCODE

DECODE

VID

VOD

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