AD5725 Analog Devices, AD5725 Datasheet - Page 17

• Manufacturer Part Number: AD5725
• Description: Quad, 12-Bit, Parallel Input, Unipolar/Bipolar, Voltage Output DAC
• Manufacturer: Analog Devices

Specifications of AD5725

• Resolution (bits): 12bit
• Dac Update Rate: 144kSPS
• Dac Settling Time: 7µs
• Max Pos Supply (v): +15V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Par

POWER SUPPLIES
Power supplies required are AV
supply can be set between −15 V and 0 V. AV
supply; its operating range is between +5 V and +15 V.
V
It is normally connected to +5 V. This pin is a logic reference
input only. It does not supply current to the device. If the readback
function is not used, V
not supply current to the AD5725, it does supply current to the
digital outputs when the readback function is used.
REFERENCE CONFIGURATION
Output voltage ranges can be configured as either unipolar or
bipolar, and within these choices, a wide variety of options
exists. The unipolar configuration can be either a positive or a
negative voltage output, and the bipolar configuration can be
either symmetrical or nonsymmetrical.
L
BALANCE
GAIN
100kΩ
INPUT
is the digital output supply voltage for the readback function.
100kΩ
ADR01
+15V
OUTPUT
TRIM
12
5
Figure 28. Symmetrical Bipolar Operation
+
AD688 FOR ±10V
AD588 FOR ±5V
6
+15V
8
Figure 27. Unipolar +10 V Operation
39kΩ
4
10kΩ
13
+10V OPERATION
L
OP1177
can be left open-circuit. While V
±5 OR ±10V OPERATION
7
1µF
0.2µF
14
15
3
1
SS
, AV
0.2µF
0.2µF
6.2Ω
6.2Ω
V
V
REFN
REFP
DD
, and V
AD5725
V
V
AD5725
REFP
REFN
AV
+15V
AV
–15V
AV
DD
AV
+15V
–15V
L
DD
SS
DD
. The AV
SS
is the positive
0.1µF
10µF
0.1µF
10µF
SS
L
does
Rev. A | Page 17 of 20
Figure 28 (Symmetrical Bipolar Operation) shows the AD5725
configured for ±10 V operation. See the
full explanation of reference operation. Adjustments may not be
required for many applications since the AD688 is a very high
accuracy reference. However, if additional adjustments are
required, adjust the AD5725 full scale first. Begin by loading the
digital full-scale code (0xFFF). Then, adjust the gain adjust
potentiometer to attain a DAC output voltage of 9.9976 V.
Then, adjust the balance adjust to set the mid-scale output
voltage to 0.000 V.
The 0.2 μF bypass capacitors shown at the reference inputs in
Figure 28 should be used whenever ±10 V references are used.
Applications with single references or references to ±5 V may
not require the 0.2 μF bypassing. The 6.2 Ω resistor in series
with the output of the reference amplifier is to keep the amplifier
from oscillating with the capacitive load. We have found that
this is large enough to stabilize this circuit. Larger resistor
values are acceptable, provided that the drop across the resistor
does not exceed a V
maximum current of 2.75 mA, the resistor should be under
200 Ω for the loading of a single AD5725.
Using two separate references is not recommended. Having two
references can cause different drifts with time and temperature,
whereas with a single reference, most drifts will track.
Unipolar positive full-scale operation can usually be set with a
reference with the correct output voltage. This is preferable to
using a reference and dividing down to the required value. For a
10 V full-scale output, the circuit can be configured as shown in
Figure 29. In this configuration, the full-scale value is set first by
adjusting the 10 kΩ resistor for a full-scale output of 9.9976 V.
BE
. Assuming a minimum V
AD688
BE
data sheet for a
of 0.6 V and a
AD5725