Datasheet

Data Sheet AD5696R/AD5695R/AD5694R
Rev. B | Page 27 of 32
APPLICATIONS INFORMATION
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD5696R/AD5695R/
AD5694R 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.
AD5696R/AD5695R/AD5694R TO ADSP-BF531
INTERFACE
The I
2
C interface of the AD5696R/AD5695R/AD5694R is
designed to be easily connected to industry-standard DSPs and
microcontrollers. Figure 58 shows the AD5696R/AD5695R/
AD5694R connected to the Analog Devices Blackfin® DSP. The
Blackfin has an integrated I
2
C port that can be connected
directly to the I
2
C pins of the AD5696R/AD5695R/AD5694R.
Figure 58. ADSP-BF531 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. The PCB on which the
AD5696R/AD5695R/AD5694R are mounted should be
designed so that the AD5696R/AD5695R/AD5694R lie
on the analog plane.
The AD5696R/AD5695R/AD5694R 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 capacitor 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.
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 AD5696R/AD5695R/AD5694R LFCSP models have 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 59) to provide a natural heat sinking effect.
Figure 59. 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 struc-
ture of the AD5696R/AD5695R/AD5694R
makes the part ideal
for isolated interfaces because the number of interface lines is
kept to a minimum. Figure 60 shows a 4-channel isolated
interface to the AD5696R/AD5695R/AD5694R using an
ADuM1400. For further information, visit
http://www.analog.com/icouplers.
Figure 60. Isolated Interface
ADSP-BF531
SCL
GPIO1
SDAGPIO2
LDACPF9
RESETPF8
AD5696R/
AD5695R/
AD5694R
10486-164
AD5696R/
AD5695R/
AD5694R
GND
PLANE
BOARD
10486-166
ENCODE
SERIAL
CLOCK IN
CONTROLLER
ADuM1400
1
SERIAL
DATA OUT
RESET OUT
LOAD DAC
OUT
DECODE
TO
SCL
TO
SDA
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.
10486-167