EVAL-AD5765EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD5765EBZ' PDF : 28 Pages View PDF
Data Sheet
AD5765
APPLICATIONS INFORMATION
TYPICAL OPERATING CIRCUIT
Figure 29 shows the typical operating circuit for the AD5765.
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 29, AVDD is connected to +5 V and AVSS is connected
to −5 V. In Figure 29, AGNDx is connected to REFGND.
+5V
10µF
100nF
ADR420
2 VIN VOUT 6
GND
4
+5V –5V
10µF
100nF
10µF
100nF
100nF
BIN/2sCOMP
+5V
32 31 30 29 28 27 26 25
SYNC
SCLK
SDIN
SDO
LDAC
D0
D1
1 SYNC
2 SCLK
3 SDIN
4 SDO
5 CLR
6 LDAC
7 D0
8 D1
AD5765
AGNDA 24
VOUTA 23
VOUTB 22
AGNDB 21
AGNDC 20
VOUTC 19
VOUTD 18
AGNDD 17
VOUTA
VOUTB
VOUTC
VOUTD
RSTOUT
RSTIN
9 10 11 12 13 14 15 16
10µF
100nF
NC = NO CONNECT
+5V
10µF
+5V –5V
Figure 29. Typical Operating Circuit
PRECISION VOLTAGE REFERENCE SELECTION
To achieve the optimum performance from the AD5765 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 AD5765 has two reference
inputs, REFAB and REFCD. 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 may 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 21. Some Precision References Recommended for Use with the AD5765
Part No. Initial Accuracy (mV Max) Long-Term Drift (ppm Typ) Temp Drift (ppm/°C Max)
ADR430 ±1
40
3
ADR420 ±1
50
3
0.1 Hz to 10 Hz Noise (µV p-p Typ)
3.5
1.75
Rev. C | Page 25 of 28
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