Datasheet

AD5066
Rev. A | Page 21 of 24
APPLICATIONS INFORMATION
USING A REFERENCE AS A POWER SUPPLY
Because the supply current required by the AD5066 is extremely
low, an alternative option is to use a voltage reference to supply
the required voltage to the parts (see Figure 47). This is espe-
cially useful if the power supply is quite noisy or if the system
supply voltages are at some value other than 5 V or 3 V, for
example, 15 V. The voltage reference outputs a steady supply
voltage for the AD5066. If the low dropout REF195 is used, it
must supply 2.5 mA of current to the AD5066 with no load on
the output of the DAC.
SYNC
SCLK
DIN
15V
5V 4.5V
V
OUT
x = 0V TO 4.5V
V
DD
V
REF
REF195
AD5066
3-WIRE
SERIAL
INTERFACE
REF194
06845-013
Figure 47. REF195 as a Power Supply to the AD5066
BIPOLAR OPERATION
The AD5066 has been designed for single-supply operation,
but a bipolar output range is also possible using the circuit in
Figure 48. The circuit gives an output voltage range of ±5 V.
Rail-to-rail operation at the amplifier output is achieved
using an AD8638 or AD8639 the output amplifier.
The output voltage for any input code can be calculated as
follows:












×−






+
×






×=
R1
R2
V
R1
R2R1D
VV
DDDD
O
536,65
where:
D = the input code in decimal (0 to 65,535).
V
DD
= 5 V.
R1 = R2 = 10 kΩ.
V5
536,65
10
−






×
=
D
V
O
This is an output voltage range of ±5 V, with 0x0000 corre-
sponding to a −5 V output, and 0xFFFF corresponding to a
+5 V output.
3-WIRE
SERIAL INTERFACE
R2 = 10kΩ
+5V
AD820/
OP295
+5.5V
+5V
AD5066
V
DD
V
OUT
R1 = 10kΩ
V
REF
±5V
0.1µF
10µF
V
REF
–5V
06845-014
Figure 48. Bipolar Operation with the AD5066
USING THE AD5066 WITH A GALVANICALLY
ISOLATED INTERFACE
In process control applications in industrial environments,
it is often necessary to use a galvanically isolated interface to
protect and isolate the controlling circuitry from any hazardous
common-mode voltages that can occur in the area where
the DAC is functioning. iCoupler® provides isolation in excess
of 2.5 kV. The AD5066 uses a 3-wire serial logic interface, so
the ADuM1300 three-channel digital isolator provides the
required isolation (see Figure 49). The power supply to the
part also needs to be isolated, which 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 AD5066.
0.1µF
GND
DIN
SYNC
SCLK
POWER
10µF
SDI
SCLK
DATA
AD5066
V
OUT
x
V
OB
V
OA
V
OC
V
DD
V
IC
V
IB
V
IA
ADuM1300
5V
REGULATOR
06845-015
Figure 49. AD5066 with a Galvanically Isolated Interface