Datasheet

AD5541A
Rev. A | 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.
0
8516-040
AD5541A
CS
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.
0
8516-041
AD5541A
CS
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 F
in parallel with 0.1 F on each supply located as close to the
package as possible, ideally right up against the device. The
10 F capacitors are the tantalum bead type. The 0.1 F 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
ADuM1400
1
SERIAL
DATA OUT
SYNC OUT
LOAD DAC
OUT
DECODE
TO
SCLK
TO
DIN
TO
CS
TO
LDAC
V
IA
V
OA
ENCODE DECODE
V
IB
V
OB
ENCODE DECODE
V
IC
V
OC
ENCODE DECODE
V
ID
V
OD
08516-042
1
ADDITIONAL PINS OMITTED FOR CLARITY.
Figure 34. Isolated Interface