AD5726 Analog Devices, AD5726 Datasheet - Page 15

• Manufacturer Part Number: AD5726
• Description: Quad, 12-Bit, Serial Input, Unipolar/Bipolar, Voltage Output DAC
• Manufacturer: Analog Devices

Specifications of AD5726

• Resolution (bits): 12bit
• Dac Update Rate: 111kSPS
• Dac Settling Time: 9µs
• Max Pos Supply (v): +15.75V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

APPLICATIONS INFORMATION
POWER-UP SEQUENCE
To prevent CMOS latch-up conditions, powering AV
and GND prior to any reference voltages is recommended. The
ideal power-up sequence is GND, AV
the digital inputs. Noncompliance with the power-up sequence
over an extended period can elevate the reference currents and
eventually damage the device. On the other hand, if the non-
compliant power-up sequence condition is as short as a few
milliseconds, the device can resume normal operation without
damage once AV
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 (as
shown in Figure 25) or a negative voltage output. The bipolar
configuration can be either symmetrical (as shown in Figure 26)
or nonsymmetrical.
INPUT
BALANCE
GAIN
100kΩ
ADR01
+15V
100kΩ
OUTPUT
TRIM
12
5
+
AD688 FOR ±10V
AD588 FOR ±5V
Figure 26. Symmetrical Bipolar Operation
6
+15V
8
DD
Figure 25. Unipolar +10 V Operation
39kΩ
10kΩ
4
/AV
13
+10V OPERATION
OP1177
SS
7
are powered up.
1µF
14
15
0.2µF
3
1
0.2µF
0.2µF
6.2Ω
6.2Ω
±5 OR ±10V OPERATION
V
V
REFN
REFP
SS
, AV
AD5726
V
V
AD5726
+15V
AV
AV
–15V
REFP
REFN
AV
+15V
AV
–15V
DD
DD
SS
DD
SS
, V
REFP
, V
0.1µF║10µF
DD
0.1µF║10µF
REFN
, AV
, and
SS
Rev. B | Page 15 of 20
,
Figure 26 (symmetrical bipolar operation) shows the AD5726
configured for ±10 V operation. See the
full explanation of the reference operation.
Adjustments may not be necessary for many applications
because the AD688 is a very high accuracy reference. However,
if additional adjustments are required, adjust the AD5726 full-
scale first. Begin by loading the digital full-scale code (0xFFF).
Then, modify the gain adjust potentiometer to attain a DAC
output voltage of 9.9976 V. Next, alter the balance adjust to set
the midscale output voltage to 0.000 V.
The 0.2 μF bypass capacitors shown at their reference inputs in
Figure 26 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 keeps the amplifier
from oscillating with the capacitive load. This has been found
to be large enough to stabilize this circuit. Larger resistor values
are acceptable if the drop across the resistor does not exceed a V
Assuming a minimum V
2.75 mA, the resistor should be under 200 Ω for the loading of a
single AD5726.
Using two separate references is not recommended. Having two
references may cause different drifts with time and temperature,
whereas with a single reference, most drifts track.
Unipolar positive full-scale operation can usually be set by 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 25. In this configuration, the full-scale value is first set
by adjusting the 10 kΩ resistor for a full-scale output of 9.9976 V.
Figure 27 shows the AD5726 configured for −10 V to 0 V opera-
tion. An
output that is connected directly to V
0.1µF║10µF
ADR01
and
Figure 27. Unipolar −10 V Operation
AD5726
AV
AV
+15V
–15V
OP1177
DD
V
V
SS
REFN
REFP
BE
+15V
0V TO –10V OPERATION
of 0.6 V and a maximum current of
are configured to produce a −10 V
0.2µF
V
TEMP
REFP
IN
ADR01
GND
for the reference voltage.
U1
AD688
V
TRIM
OUT
OP1177
U2
data sheet for a
+15V
–15V
V+
V–
AD5726
BE
.