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AD5313R

Data Sheet

Rev. B | Page 24 of 26

APPLICATIONS INFORMATION

MICROPROCESSOR INTERFACING

Microprocessor interfacing to the AD5313R is achieved via a

serial bus using a standard protocol that is compatible with DSP

processors and microcontrollers. The communications channel

requires a 3-wire or 4-wire interface consisting of a clock signal,

a data signal, and a synchronization signal. The device requires

a 24-bit data-word with data valid on the rising edge of SYNC.

AD5313R TO ADSP-BF531 INTERFACE

The SPI interface of the AD5313R is designed to be easily

connected to industry-standard DSPs and microcontrollers.

Figure 47 shows the AD5313R connected to an Analog Devices

Blackfin® DSP. The Blackfin has an integrated SPI port that can

be connected directly to the SPI pins of the AD5313R.

Figure 47. AD5313R to ADSP-BF531 Interface

AD5313R TO SPORT INTERFACE

The Analog Devices ADSP-BF527 has one SPORT serial port.

Figure 48 shows how one SPORT interface can be used to

control the AD5313R.

Figure 48. AD5313R to SPORT Interface

LAYOUT GUIDELINES

In any circuit where accuracy is important, careful considera-

tion of the power supply and ground return layout helps to ensure

the rated performance. Design the PCB on which the AD5313R

is mounted such that the AD5313R lies on the analog plane.

Provide the AD5313R with 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 capa-

citors are of the tantalum bead type. Use a 0.1 µF capacitor with

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 AD5313R has an exposed paddle beneath the device.

Connect this paddle 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 paddle

on the bottom of the 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 49) to provide a natural heat sinking effect.

Figure 49. 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

Coupler® products from Analog Devices provide voltage isolation

in excess of 2.5 kV. The serial loading structure of the AD5313R

makes the part ideal for isolated interfaces because the number of

interface lines is kept to a minimum. Figure 50 shows a 4-channel

isolated interface to the AD5313R using an ADuM1400. For

more information, visit http://www.analog.com/icouplers.

Figure 50. Isolated Interface

ADSP-BF531

SYNC

SPISELx

SCLK

SCK

SDIN

MOSI

LDAC

PF9

RESET

PF8

AD5313R

ADSP-BF527

SYNC

SPORT_TFS

SCLK

SPORT_TSCK

SDIN

SPORT_DTO

LDAC

GPIO0

RESET

GPIO1

AD5313R

GND

PLANE

BOARD

ENCODE

SERIAL

CLOCK IN

CONTROLLER

ADuM14001

SERIAL

DATA OUT

SYNC OUT

LOAD DAC

OUT

DECODE

SCLK

SDIN

SYNC

LDAC

VIA

VOA

ENCODE

DECODE

VIB

VOB

ENCODE

DECODE

VIC

VOC

ENCODE

DECODE

VID

VOD

1ADDITIONAL PINS OMITTED FOR CLARITY.

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