Datasheet

AD5551/AD5552
Rev. A | Page 15 of 16
APPLICATIONS INFORMATION
OPTOCOUPLER INTERFACE
The digital inputs of the AD5551/AD5552 are Schmitt-
triggered, so they can accept slow transitions on the digital
input lines. This makes these parts ideal for industrial applica-
tions where it may be necessary that the DAC is isolated from
the controller via optocouplers. Figure 29 illustrates such an
interface.
10µF
0.1µF
V
OUT
V
DD
POWER
GND
5V
REGULATOR
AD5551/
AD5552
10kΩ
V
DD
CS
CS
DIN
10kΩ
V
DD
DIN
10kΩ
V
DD
SCLK SCLK
01943-029
Figure 29. AD5551/AD5552 in an Optocoupler Interface
DECODING MULTIPLE AD5551/AD5552S
The
CS
pin of the AD5551/AD5552 can be used to select one of
a number of DACs. All devices receive the same serial clock and
serial data, but only one device receives the
CS
signal at any one
time. The DAC addressed is determined by the decoder. There
is some digital feedthrough from the digital input lines. Using a
burst clock minimizes the effects of digital feedthrough on the
analog signal channels. shows a typical circuit. Figure 30
AD5551/
AD5552
CS
DIN
SCLK
V
OUT
AD5551/
AD5552
CS
DIN
SCLK
V
OUT
AD5551/
AD5552
CS
DIN
SCLK
V
OUT
AD5551/
AD5552
CS
DIN
SCLK
V
OUT
V
DD
DGND
EN
CODED
ADDRESS
SCLK
DIN
ENABLE
DECODER
01943-030
Figure 30. Addressing Multiple AD5551/AD5552s