
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 (se
e 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 dropou
t 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
VOUTx = 0V TO 4.5V
VDD
VREF
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
The output voltage for any input code can be calculated as
follows:
×
+
×
×
=
R1
R2
V
R1
R2
R1
D
V
DD
O
536
,
65
where:
D = the input code in decimal (0 to 65,535).
VDD = 5 V.
R1 = R2 = 10 k.
V
5
536
,
65
10
×
=
D
VO
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 = 10k
+5V
AD820/
OP295
+5.5V
+5V
AD5066
VDD
VOUT
R1 = 10k
VREF
±5V
0.1F
10F
VREF
–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
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.
0.1F
GND
DIN
SYNC
SCLK
POWER
10F
SDI
SCLK
DATA
AD5066
VOUTx
VOB
VOA
VOC
VDD
VIC
VIB
VIA
ADuM1300
5V
REGULATOR
06845-
015
Figure 49. AD5066 with a Galvanically Isolated Interface