AD5025 Analog Devices, AD5025 Datasheet - Page 24

• Manufacturer Part Number: AD5025
• Description: Fully Accurate 12-Bit VOUT DAC SPI Interface 2.7 V to 5.5 V in a TSSOP
• Manufacturer: Analog Devices

Specifications of AD5025

• Resolution (bits): 12bit
• Dac Update Rate: 1.5MSPS
• Dac Settling Time: 10.7µs
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

AD5025/AD5045/AD5065
APPLICATIONS INFORMATION
USING A REFERENCE AS A POWER SUPPLY FOR
THE AD5025/AD5045/AD5065
Because the supply current required by the AD5025/AD5045/
AD5065 is extremely low, an alternative option is to use a voltage
reference to supply the required voltage to the parts (see Figure 50).
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 or
3 V, for example, 15 V. The voltage reference outputs a steady
supply voltage for the AD5025/AD5045/AD5065. If the low
dropout
the AD5025/AD5045/AD5065 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 kΩ load on the DAC output) is
The load regulation of the REF195 is typically 2 ppm/mA,
which results in a 3 ppm (15 μV) error for the 1.5 mA current
drawn from it. This corresponds to a 0.196 LSB error.
BIPOLAR OPERATION USING THE
AD5025/AD5045/AD5065
The AD5025/AD5045/AD5065 is designed for single-supply
operation, but a bipolar output range is also possible using the
circuit in Figure 51. The circuit gives an output voltage range of
±5 V. Rail-to-rail operation at the amplifier output is achievable
using an
The output voltage for any input code can be calculated as
follows:
where D represents the input code in decimal (0 to 65,535).
With V
INTERFACE
Figure 50. REF195 as Power Supply to the AD5025/AD5045/AD5065
500 μA + (5 V/5 kΩ) = 1.5 mA
V
V
SERIAL
3-WIRE
O
O
DD
REF195


AD820
= 5 V, R1 = R2 = 10 kΩ,






V
10
65
DD
,

536
SYNC
SCLK

D
DIN
or an
is used, it must supply 500 μA of current to



15V



65

D
,
REF195
536
OP295
5
V







as the output amplifier.
R1
5V
R1

AD5025/
AD5045/
AD5065
R2
V
DD




V
DD

V
OUT



R2
R1
x = 0V TO 5V






Rev. 0 | Page 24 of 28
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.
USING THE AD5025/AD5045/AD5065 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 AD5025/AD5045/AD5065 use a 3-wire serial logic interface,
so the
required isolation (see Figure 52). The power supply to the part
also needs to be isolated, which is achieved by using a transformer.
On the DAC side of the transformer, a 5 V regulator provides the
5 V supply required for the AD5025/AD5045/AD5065.
+5V
SCLK
DATA
Figure 52. AD5025/AD5045/AD5065 with a Galvanically Isolated Interface
POWER
SDI
Figure 51. Bipolar Operation with the AD5025/AD5045/AD5065
ADuM1300
10µF
V
V
V
IA
IB
IC
ADuM1300
0.1µF
three-channel digital isolator provides the
SERIAL INTERFACE
V
V
V
OA
OB
OC
V
DD
AD5025/
AD5045/
R1 = 10kΩ
AD5065
3-WIRE
REGULATOR
V
OUT
5V
SYNC
DIN
SCLK
AD5025/
AD5045/
AD5065
GND
V
DD
AD820/
OP295
R2 = 10kΩ
+5V
–5V
V
OUT
10µF
x
0.1µF
±5V