AD5330_08 datasheet(21/28 Pages) AD

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AD5330/AD5331/AD5340/AD5341

Rev. A | Page 21 of 28

APPLICATIONS INFORMATION

TYPICAL APPLICATION CIRCUITS

The AD5330/AD5331/AD5340/AD5341 can be used with

a wide range of reference voltages, especially if the reference

inputs are configured to be 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

can be used with a fixed, precision reference voltage. Figure 43

shows a typical setup for the devices when using an external

reference connected to the unbuffered reference inputs. If the

reference inputs are unbuffered, the reference input range is

from 0.25 V to VDD, but if the on-chip reference buffers are

used, the reference range is reduced. Suitable references for 5 V

operation are the AD780 and REF192. For 2.5 V operation, a

suitable external reference is the AD589, a 1.23 V band gap

reference.

AD5330/AD5331/

AD5340/AD5341

VOUT

VDD = 2.5V TO 5.5V

VDD

GND

VREF

GND

EXT

REF

0.1µF

10µF

VOUT

VIN

AD780/REF192

WITH VDD = 5V

AD589 WITH VDD = 2.5V

Figure 43. AD5330/AD5331/AD5340/AD5341 Using 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 using

a 5 V reference such as the ADP667, as shown in Figure 44.

AD5330/AD5331/

AD5340/AD5341

GND SHDN

VOUT

ADP667

VSET

6V TO 16V

VOUT

VDD

VIN

GND

VREF

0.1µF

10µF

Figure 44. Using an ADP667 as Power and Reference to

AD5330/AD5331/AD5340/AD5341

BIPOLAR OPERATION USING THE AD5330/AD5331/

AD5340/AD5341

The AD5330/AD5331/AD5340/AD5341 are designed for

single-supply operation, but bipolar operation is achievable

using the circuit shown in Figure 45. The circuit shown has

been configured to achieve an output voltage range of –5 V <

VO < +5 V. Rail-to-rail operation at the amplifier output is

achievable using an AD820 or OP295 as the output amplifier.

The output voltage for any input code can be calculated as follows:

= [(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 = 2.5 V.

R1 = R3 = 10 kΩ.

R2 = R4 = 20 kΩ and VDD = 5 V.

VO = (10 × D/2N) − 5.

VDD = 5V

0.1µF

10µF

20kΩ

10kΩ

20kΩ

GND

VO = ±5V

+5V

–5V

AD5330/AD5331/

AD5340/AD5341

VREF

VOUT

VDD

GND

EXT

REF

VOUT

VIN

AD780/REF192

WITH VDD = 5V

AD589 WITH VDD = 2.5V

0.1µF

Figure 45. Bipolar Operation using the AD5330/AD5331/AD5340/AD5341

DECODING MULTIPLE AD5330/AD5331/

AD5340/AD5341

The CS pin on these devices can be used in applications to

decode a number of DACs. In this application, all DACs in the

system receive the same data and WR pulses, but only CS to one

of the DACs is active at any one time, so data is only written to

the DAC whose CS is low. If multiple AD5341s are being used, a

common HBEN line is also required to determine if the data is

written to the high byte or low byte register of the selected DAC.

The 74HC139 is used as a 2-line to 4-line decoder to address

any of the DACs in the system. To prevent timing errors, the

enable input should be brought to its inactive state while the

coded address inputs are changing state. Figure 46 shows a

diagram of a typical setup for decoding multiple devices in a

system. Once data has been written sequentially to all DACs in

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