AD5024/AD5044/AD5064
Data Sheet
Rev. F | Page 26 of 28
APPLICATIONS INFORMATION
USING A REFERENCE AS A POWER SUPPLY
Because the supply current required by the AD5024/AD5044/
AD5064/AD5064-1 is extremely low, an alternative option is to
use a voltage reference to supply the required voltage to the parts
(s
ee Figure 56). This is especially useful if the power supply is
quite noisy or if the system supply voltages are at some value
other than 5 V (for example, 15 V). The voltage reference outputs
a steady supply voltage for the AD5024/AD5044/AD5064/
AD5064-1. If the low dropou
t REF195 is used, it must supply
3 mA of current to the AD5024/AD5044/AD5064/AD5064-1,
with no load on the output of the DAC. When the DAC output is
loaded, the REF195 also needs to supply the current to the load.
The total current required (with a 5 k load on the DAC output) is
3 mA + (5 V/5 k) = 4 mA
The load regulation of the REF195 is typically 2 ppm/mA,
which results in a 3 ppm (15 V) error for the 4 mA current
drawn from it. This corresponds to a 0.196 LSB error.
SYNC
SCLK
DIN
15V
5V
VOUT = 0V TO 5V
VDD
REF195
AD5024/
AD5044/
AD5064/
AD5064-1
3-WIRE
SERIAL
INTERFACE
06803-
016
Figure 56. REF195 as Power Supply to the AD5024/AD5044/AD5064/AD5064-1
BIPOLAR OPERATION
The AD5024/AD5044/AD5064/AD5064-1 have been designed
for single-supply operation, but a bipolar output range is also
possible using the circuit shown
in Figure 57. The circuit gives an
output voltage range of ±5 V. Rail-to-rail operation at the
as the output amplifier.
Assuming VDD = VREF, the output voltage for any input code can
be calculated as follows:
×
+
×
×
=
R1
R2
V
R1
R2
R1
D
V
DD
OUT
536
,
65
where D represents the input code in decimal (0 to 65,535).
With VDD = 5 V, R1 = R2 = 10 k,
V
5
536
,
65
10
×
=
D
VOUT
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.
06803-
017
3-WIRE
SERIAL INTERFACE
R2 = 10k
+5V
AD5024/
AD5044/
AD5064/
AD5064-1
VDD
VOUTA
R1 = 10k
±5V
0.1F
10F
VREFA
–5V
5V
VREF
AD8638/
AD8639
Figure 57. Bipolar Operation
USING THE AD5024/AD5044/AD5064/AD5064-1
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 AD5024/AD5044/AD5064/AD5064-1 use a 3-wire
serial logic interface, so the ADuM1300 three-channel digital
isolator provides the required isolation (see
Figure 58). 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 AD5024/
AD5044/AD5064/AD5064-1.
0.1F
GND
DIN
SYNC
SCLK
POWER
10F
SDI
SCLK
DATA
AD5024/
AD5044/
AD5064/
AD5064-1
VOUTx
VOB
VOA
VOC
VDD
VIC
VIB
VIA
ADuM1300
5V
REGULATOR
06803-
018
Figure 58. AD5024/AD5044/AD5064/AD5064-1 with a Galvanically Isolated
Interface