Datasheet

Data Sheet AD5697R
Rev. 0 | Page 25 of 28
APPLICATIONS INFORMATION
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD5697R 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.
AD5697R-TO-ADSP-BF531 INTERFACE
The I
2
C interface of the AD5697R is designed to be easily
connected to industry-standard DSPs and microcontrollers.
Figure 51 shows the AD5697R connected to the Analog Devices
Blackfin® DSP (ADSP-BF531). The Blackfin has an integrated I
2
C
port that can be connected directly to the I
2
C pins of the AD5697R.
Figure 51. ADSP-BF531 Interface to the AD5338R
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 AD5697R is mounted so that the AD5697R lies on
the analog plane.
The AD5697R 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 capacitor
is the 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 that 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 AD5697R LFCSP model 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 52) to provide a natural heat sinking effect.
Figure 52. 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. iCoupler®
products from Analog Devices provide voltage isolation in
excess of 2.5 kV. The serial loading structure of the AD5697R
makes the part ideal for isolated interfaces because the number of
interface lines is kept to a minimum. Figure 53 shows a 4-channel
isolated interface to the AD5697R using the ADuM1400. For
further information, visit http://www.analog.com/icouplers.
Figure 53. Isolated Interface
ADSP-BF531
SCLGPIO1
SDA
GPIO2
LDACPF9
RESETPF8
AD5697R
11253-052
AD5697R
GND
PLANE
BOARD
11253-053
ENCODE
SERIAL
CLOCK IN
CONTROLLER
ADuM1400
1
SERIAL
DATA OUT
RESET OUT
LOAD DAC
OUT
DECODE
TO
SCLK
TO
SDIN
TO
RESET
TO
LDAC
V
IA
V
OA
ENCODE DECODE
V
IB
V
OB
ENCODE DECODE
V
IC
V
OC
ENCODE DECODE
V
ID
V
OD
1
ADDITIONAL PINS OMITTED FOR CLARITY.
11253-054