AD5763CSUZ datasheet(25/31 Pages) AD

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Preliminary Technical Data

AD5763

Rev. PrA | Page 25 of 31

APPLICATIONS INFORMATION

TYPICAL OPERATING CIRCUIT

Figure 35 shows the typical operating circuit for the AD5763.

The only external components needed for this precision 16-bit

DAC are a reference voltage source, decoupling capacitors on

the supply pins and reference inputs, and an optional short-

circuit current setting resistor. Because the device incorporates

reference buffers, it eliminates the need for an external bipolar

reference and associated buffers. This leads to an overall savings

in both cost and board space.

In Figure 35, AVDD is connected to +5 V and AVSS is connected

to −5 V. In Figure 35, AGNDA is connected to REFGND.

10 11

13 14 15

32 31 30

29 28 27 26

AD5763

SYNC

SCLK

SDIN

SDO

LDAC

CLR

VOUTA

AGNDA

VOUTB

AGNDB

SYNC

SCLK

SDIN

SDO

LDAC

RSTOUT

RSTIN

BIN/2sCOMP

+5V

–5V

NC = NO CONNECT

+5V –5V

VOUTA

VOUTB

100nF

10µF

100nF

10µF

ADR420

GND

VOUT

VIN

+5V

100nF

10µF

Figure 35. Typical Operating Circuit

Precision Voltage Reference Selection

To achieve the optimum performance from the AD5763 over its

full operating temperature range, a precision voltage reference

must be used. Thought should be given to the selection of a

precision voltage reference. The AD5763 has two reference

inputs, REFA and REFB. The voltages applied to the reference

inputs are used to provide a buffered positive and negative

reference for the DAC cores. Therefore, any error in the voltage

reference is reflected in the outputs of the device.

There are four possible sources of error to consider when

choosing a voltage reference for high accuracy applications:

initial accuracy, temperature coefficient of the output voltage,

long term drift, and output voltage noise.

Initial accuracy error on the output voltage of an external refer-

ence could lead to a full-scale error in the DAC. Therefore, to

minimize these errors, a reference with low initial accuracy

error specification is preferred. Choosing a reference with an

output trim adjustment, such as the ADR430, allows a system

designer to trim system errors out by setting the reference

voltage to a voltage other than the nominal. The trim adjust-

ment can also be used at temperature to trim out any error.

Long-term drift is a measure of how much the reference output

voltage drifts over time. A reference with a tight long-term drift

specification ensures that the overall solution remains relatively

stable over its entire lifetime.

The temperature coefficient of a reference output voltage affects

INL, DNL, and TUE. A reference with a tight temperature

coefficient specification should be chosen to reduce the

dependence of the DAC output voltage on ambient conditions.

In high accuracy applications, which have a relatively low noise

budget, reference output voltage noise needs to be considered.

Choosing a reference with as low an output noise voltage as

practical for the system resolution required is important.

Precision voltage references such as the ADR420 (XFET® design)

produce low output noise in the 0.1 Hz to 10 Hz region.

However, as the circuit bandwidth increases, filtering the output

of the reference may be required to minimize the output noise.

Table 19. Some Precision References Recommended for Use with the AD5763

Part No.

Initial Accuracy (mV Max)

Long-Term Drift (ppm Typ)

Temp Drift (ppm/°C Max)

0.1 Hz to 10 Hz Noise (µV p-p Typ)

ADR430

±1

3.5

ADR420

±1

1.75

ADR390

±4

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