Datasheet

AD5293
Rev. D | Page 22 of 24
APPLICATIONS INFORMATION
HIGH VOLTAGE DAC
The AD5293 can be configured as a high voltage DAC, with an
output voltage as high as 33 V. The circuit is shown in Figure 51.
The output is
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+××=
1
2
1V2.1
1024
)(
R
RD
DV
OUT
(4)
where
D is the decimal code from 0 to 1023.
AD5293
U2
AD8512
V+
V–
AD8512
V
OUT
V
DD
U1B
V
DD
R
BIAS
A
DR512
D1
R
2
R
1
B
20k
U1A
07675-153
Figure 51. High Voltage DAC
PROGRAMMABLE VOLTAGE SOURCE WITH
BOOSTED OUTPUT
For applications that require high current adjustments, such as
a laser diode or turnable laser, a boosted voltage source can be
considered (see Figure 52).
W
SIGNAL
C
C
R
BIAS
LD
V
IN
A
B
V
OUT
U1
AD5293
U3 2N7002
U2
I
L
OP184
07675-155
Figure 52. 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 AD5293 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 53. The improved
±1% resistor 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
+×+
×
×
+
=
−
(5)
AD5293
U1
V
OUT
B
R
2
20k
R
1
R
3
±1%
OP1177
V+
V–
V
DD
V
DD
U2
07675-154
Figure 53. Optimizing Resolution
VARIABLE GAIN INSTRUMENTATION AMPLIFIER
The AD8221 in conjunction with the AD5293 and the ADG1207,
as shown in Figure 54, make an excellent instrumentation
amplifier for use in data acquisition systems. The data acquisition
system is low distortion and low noise enable it to condition
signals in front of a variety of ADCs.
AD8221
AD5293
+V
IN1
V
DD
V
OUT
V
SS
A
DG1207
+V
IN4
–V
IN1
–V
IN4
07675-156
Figure 54. Data Acquisition System
The gain can be calculated by using Equation 6, as follows:
AB
RD
DG
×
+=
)1024(
k4.49
1)(
(6)