Datasheet

AD5346/AD5347/AD5348
Rev. 0 | Page 19 of 24
APPLICATIONS INFORMATION
TYPICAL APPLICATION CIRCUITS
The AD5346/AD5347/AD5348 can be used with a wide range
of reference voltages, especially if the reference inputs are
configured as unbuffered, in which case the devices offer full,
one-quadrant multiplying capability over a reference range of
0.25 V to V
DD
. More typically, these devices may be used with a
fixed, precision reference voltage. Figure 41 shows a typical
setup for the devices when using an external reference
connected to the reference inputs. Suitable references for 5 V
operation are the AD780, ADR381, and REF192 (2.5 V refer-
ences). For 2.5 V operation, suitable external references are the
AD589 and the AD1580 (1.2 V band gap references).
AD5346/AD5347/
AD5348
V
OUT
*
0.1µF
V
DD
= 2.5V to 5.5V
V
DD
GND
AD780/ADR381/REF192
WITH V
DD
= 5V
OR AD589/AD1580 WITH
V
DD
= 2.5V
V
REF
*
GND
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
10µF
V
OUT
V
IN
EXT
REF
03331-0-024
Figure 41. AD5346/AD5347/AD5348 Using an External Reference
DRIVING V
DD
FROM THE REFERENCE VOLTAGE
If an output range of 0 V to V
DD
is required, the simplest
solution is to connect the reference inputs to V
DD
. Because this
supply may not be very accurate and may be noisy, the devices
can be powered from the reference voltage, for example, by
using a 5 V reference such as the ADM663 or ADM666, as
shown in Figure 42.
AD5346/AD5347/
AD5348
V
OUT
*
0.1µF
6V TO 16V
V
DD
GND
V
REF
*
GND
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
10µF
V
OUT(2)
V
IN
EXT
REF
0.1µF
GND
SENSE
SHDNVSET
ADM663/ADM666
03331-0-025
Figure 42. Using an ADM663/ADM666 as Power and
Reference to the AD5346/AD5347/AD5348
BIPOLAR OPERATION USING THE
AD5346/AD5347/AD5348
The AD5346/AD5347/AD5348 have been designed for single-
supply operation, but a bipolar output range is also possible by
using the circuit shown in Figure 43. This circuit has an output
voltage range of ±5 V. Rail-to-rail operation at the amplifier
output is achievable using an AD820, an AD8519, or an OP196
as the output amplifier.
5V
EXT
REF
GND
V
OUT
R2
20kΩ
R1
10kΩ
R4
20kΩ
R3
10kΩ
±5V
+5V
–5V
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
0.1µF
0.1µF 10µF
AD820/AD8519/
OP196
V
IN
GND
AD5346/AD5347/
AD5348
V
OUT
*
V
DD
V
REF
*
03331-0-026
Figure 43. Bipolar Operation with the AD5346/ AD5347/AD5348
The output voltage for any input code can be calculated as
follows:
V
OUT
= [(1 + R4/R3) × (R2/(R1 + R2) × (2 × V
REF
× D/2
N
)] –
R4 × V
REF
/R3
where:
D is the decimal equivalent of the code loaded to the DAC.
N is the DAC resolution.
V
REF
is the reference voltage input.
with:
V
REF
= 5 V
R1 = R3 = 10 kΩ
R2 = R4 = 20 kΩ
V
DD
= 5 V
GAIN = 2
V
OUT
= (10 × D/2
N
) – 5