AD5347 datasheet(19/24 Pages) AD

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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 VDD. 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

VOUT*

0.1

µF

VDD = 2.5V to 5.5V

VDD

GND

AD780/ADR381/REF192

WITH VDD = 5V

OR AD589/AD1580 WITH

VDD = 2.5V

VREF*

GND

*ONLY ONE CHANNEL OF VREF AND VOUT SHOWN

µF

VOUT

VIN

EXT

REF

Figure 41. AD5346/AD5347/AD5348 Using an External Reference

DRIVING VDD FROM THE REFERENCE VOLTAGE

If an output range of 0 V to VDD is required, the simplest

solution is to connect the reference inputs to VDD. 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

VOUT*

0.1

µF

6V TO 16V

VDD

GND

VREF*

GND

*ONLY ONE CHANNEL OF VREF AND VOUT SHOWN

µF

VOUT(2)

VIN

EXT

REF

0.1

µF

GND

SENSE

SHDN

VSET

ADM663/ADM666

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.

EXT

REF

GND

VOUT

20k

Ω

10k

Ω

20k

Ω

10k

Ω

±5V

+5V

–5V

*ONLY ONE CHANNEL OF VREF AND VOUT SHOWN

0.1

µF

0.1

µF

AD820/AD8519/

OP196

VIN

GND

AD5346/AD5347/

AD5348

VOUT*

VDD

VREF*

Figure 43. Bipolar Operation with the AD5346/ AD5347/AD5348

The output voltage for any input code can be calculated as

follows:

VOUT

= [(1 + R4/R3) × (R2/(R1 + R2) × (2 × VREF × D/2N)] –

× VREF/R3

where:

is the decimal equivalent of the code loaded to the DAC.

is the DAC resolution.

VREF

is the reference voltage input.

with:

VREF

= 5 V

= R3 = 10 kΩ

= R4 = 20 kΩ

VDD

= 5 V

GAIN = 2

VOUT

= (10 × D/2N) – 5

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