AD5303/AD5313/AD5323
SCLK
DIN
OPTO-ISOLATED INTERFACE FOR PROCESS
CONTROL APPLICATIONS
AD5303/
SYNC AD5313/
DIN
SCLK
AD5323
V
V
DD
The AD5303/AD5313/AD5323 has a versatile 3-wire serial
interface making it ideal for generating accurate voltages in
process control and industrial applications. Due to noise, safety
requirements, or distance, it may be necessary to isolate the
AD5303/AD5313/AD5323 from the controller. This can easily
be achieved by using opto-isolators, which provides isolation
in excess of 3 kV. The serial loading structure of the AD5303/
AD5313/AD5323 makes it ideally suited for use in opto-isolated
applications. Figure 42 shows an opto-isolated interface to the
CC
1G
1A
1B
ENABLE
1Y0
1Y1
1Y2
1Y3
AD5303/
SYNC AD5313/
74HC139
CODED
ADDRESS
DIN
SCLK
AD5323
DGND
AD5303/
SYNC AD5313/
DIN
SCLK
AD5323
SYNC
AD5303/AD5313/AD5323 where DIN, SCLK, and
are
driven from opto-couplers. The power supply to the part also
needs to be isolated. This is done by using a transformer. On the
DAC side of the transformer, a 5 V regulator provides the 5 V
supply required for the AD5303/AD5313/AD5323.
AD5303/
SYNC AD5313/
DIN
SCLK
AD5323
Figure 43. Decoding Multiple AD5303/AD5313/AD5323 Devices in a System
5V
REGULATOR
10µF
0.1µF
POWER
AD5303/AD5313/AD5323 AS A DIGITALLY
PROGRAMMABLE WINDOW DETECTOR
V
DD
DD
DD
A digitally programmable upper/lower limit detector using
the two DACs in the AD5303/AD5313/AD5323 is shown in
Figure 44. The upper and lower limits for the test are loaded
to DAC A and DAC B, which, in turn, set the limits on the
CMP04. If the signal at the VIN input is not within the pro-
grammed window, an LED indicates the fail condition.
5V
10kΩ
V
DD
SCLK
SCLK
V
A
REF
V
B
REF
AD5303/AD5313/
AD5323
V
10kΩ
V
A
OUT
SYNC
0.1µF
10µF
SYNC
V
IN
1kΩ
1kΩ
V
B
OUT
FAIL
PASS
V
DD
V
V
V
A
REF
REF
V
V
A
OUT
B
REF
10kΩ
AD5303/AD5313/
1/2
CMP04
PASS/FAIL
1/6 74HC05
AD5323
DIN
DIN
GND BUF A BUF B
SYNC
SYNC
DIN
DIN
V
B
SCLK
SCLK
OUT
GND
Figure 42. AD5303/AD5313/AD5323 in an Opto-Isolated Interface
Figure 44. Window Detector Using AD5303/AD5313/AD5323
DECODING MULTIPLE AD5303/AD5313/AD5323s
SYNC
The
pin on the AD5303/AD5313/AD5323 can be used
in applications to decode a number of DACs. In this application,
all the DACs in the system receive the same serial clock and
SYNC
serial data, but only the
to one of the devices is active at
any one time, allowing access to two channels in this 8-channel
system. The 74HC139 is used as a 2-to-4 line decoder to address
any of the DACs in the system. To prevent timing errors from
occurring, the enable input should be brought to its inactive
state while the coded address inputs are changing state.
Figure 43 shows a diagram of a typical setup for decoding
multiple AD5303/AD5313/AD5323 devices in a system.
Rev. B | Page 22 of 28