Datasheet

AD5291/AD5292
Rev. D | Page 28 of 32
APPLICATIONS INFORMATION
HIGH VOLTAGE DAC
The AD5292 can be configured as a high voltage DAC, with
output voltage as high as 33 V. The circuit is shown in Figure 70.
The output is
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+××=
1
2
1V2.1
1024
)(
R
RD
DV
OUT
(7)
where D is the decimal code from 0 to 1023.
07674-153
AD5292
U2
AD8512
V+
V–
AD8512
V
OUT
V
DD
U1B
V
DD
R
BIAS
A
DR512
D1
R
2
R
1
B
20k
U1A
Figure 70. High Voltage DAC
PROGRAMMABLE VOLTAGE SOURCE WITH
BOOSTED OUTPUT
For applications that require high current adjustments such as a
laser diode or tunable laser, a boosted voltage source can be
considered; see Figure 71.
07674-155
W
SIGNAL
C
C
R
BIAS
LD
V
IN
A
B
V
OUT
U1
AD5292
U3 2N7002
U2
I
L
OP184
Figure 71. Programmable Boosted Voltage Source
In this circuit, the inverting input of the op amp forces V
OUT
to
be equal to the wiper voltage set by the digital potentiometer.
The load current is then delivered by the supply via the N-channel
FET (U3). The N-Channel FET power handling must be adequate
to dissipate (V
IN
− V
OUT
) × I
L
power. This circuit can source a
maximum of 100 mA with a 33 V supply.
HIGH ACCURACY DAC
It is possible to configure the AD5292 as a high accuracy DAC
by optimizing the resolution of the device over a specific
reduced voltage range. This is achieved by placing external
resistors on either side of the RDAC, as shown in Figure 72.
The improved ±1% R-Tolerance specification greatly reduces
error associated with matching to discrete resistors.
3
1024
)1024(
1
1024
3
)(
)(
)(
RRR
VRR
DV
AB
D
DD
AB
D
OUT
+×+
×
×
+
=
−
(8)
07674-154
AD5292
U1
V
OUT
B
R
2
20k
R
1
R
3
±1%
OP1177
V+
V–
V
DD
V
DD
U2
Figure 72. Optimizing Resolution
VARIABLE GAIN INSTRUMENTATION AMPLIFIER
The AD8221 in conjunction with the AD5291 and AD5292 and
the ADG1207, as shown in Figure 73, make an excellent
instrumentation amplifier for use in data acquisition systems.
The data acquisition system’s low distortion and low noise
enable it to condition signals in front of a variety of ADCs.
07674-156
AD8221
AD5292
+V
IN1
V
DD
V
OU
T
V
SS
A
DG1207
+V
IN4
–V
IN1
–V
IN4
Figure 73. Data Acquisition System
The gain can be calculated by using Equation 9.
()
AB
RD
DG
×
+=
1024
k4.49
1)(
(9)