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Data Sheet

AD5541A

Rev. B | Page 17 of 20

APPLICATIONS INFORMATION

MICROPROCESSOR INTERFACING

Microprocessor interfacing to the AD5541A is via a serial bus

that uses standard protocol that is compatible with DSP proces-

sors and microcontrollers. The communications channel requires

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

and a synchronization signal. The AD5541A requires a 16-bit

data-word with data valid on the rising edge of SCLK.

AD5541A TO ADSP-BF531 INTERFACE

The SPI interface of the AD5541A is designed to be easily

connected to industry-standard DSPs and microcontrollers.

Figure 32 shows how the AD5541A can be connected to the

Analog Devices, Inc., Blackfin® DSP. The Blackfin has an

integrated SPI port that can be connected directly to the SPI

pins of the AD5541A.

AD5541A

SCLK

DIN

LDAC

SPISELx

SCK

MOSI

PF9

ADSP-BF531

Figure 32. AD5541A to ADSP-BF531 Interface

AD5541A TO SPORT INTERFACE

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

Figure 33 shows how one SPORT interface can be used to

control the AD5541A.

AD5541A

SCLK

DIN

LDAC

SPORT_TFS

SPORT_TSCK

SPORT_DTO

GPIO0

ADSP-BF527

Figure 33. AD5541A to SPORT Interface

LAYOUT GUIDELINES

In any circuit where accuracy is important, careful consider-

ation of the power supply and ground return layout helps to

ensure the rated performance. Design the printed circuit board

(PCB) on which the AD5541A is mounted so that the analog

and digital sections are separated and confined to certain areas

of the board. If the AD5541A is in a system where multiple

devices require an analog ground-to-digital ground connection,

make the connection at one point only. Establish the star

ground point as close as possible to the device.

The AD5541A 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 capacitors are the tantalum bead type. The 0.1 μF capaci-

tor should 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.

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 AD5541A makes

the part ideal for isolated interfaces because the number of

interface lines is kept to a minimum. Figure 34 shows a 4-channel

isolated interface to the AD5541A using an ADuM1400. For

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

ENCODE

SERIAL

CLOCK IN

CONTROLLER

ADuM14001

SERIAL

DATA OUT

SYNC OUT

LOAD DAC

OUT

DECODE

SCLK

DIN

LDAC

VIA

VOA

ENCODE

DECODE

VIB

VOB

ENCODE

DECODE

VIC

VOC

ENCODE

DECODE

VID

VOD

1ADDITIONAL PINS OMITTED FOR CLARITY.

Figure 34. Isolated Interface

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