EVAL-AD5680EB AD [Analog Devices], EVAL-AD5680EB Datasheet - Page 15

• Manufacturer Part Number: EVAL-AD5680EB
• Description: 5 V 18-Bit nanoDAC in a SOT-23
• Manufacturer: AD [Analog Devices]

CHOOSING A REFERENCE FOR THE AD5680
To achieve the optimum performance from the AD5680,
choose a precision voltage reference carefully. The AD5680 has
only one reference input, V
input is used to supply the positive input to the DAC. Therefore
any error in the reference is reflected in the DAC.
When choosing a voltage reference for high accuracy applica-
tions, the sources of error are initial accuracy, ppm drift, long-
term drift, and output voltage noise. Initial accuracy on the
output voltage of the DAC leads to a full-scale error in the
DAC. To minimize these errors, a reference with high initial
accuracy is preferred. Also, choosing a reference with an output
trim adjustment, such as the ADR425, allows a system designer
to trim out system errors by setting a reference voltage to a
voltage other than the nominal. The trim adjustment can also
be used at temperature to trim out any error.
Table 6. Partial List of Precision References for Use with the AD5680
Part No.
ADR425
ADR395
REF195
Initial Accuracy (mV max)
±2
±6
±2
REF
. The voltage on the reference
Temp. Drift (ppm
3
25
5
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o
C max)
Long-term drift is a measurement of how much the reference
drifts over time. A reference with a tight long-term drift
specification ensures that the overall solution remains relatively
stable during its entire lifetime.
The temperature coefficient of a reference’s output voltage
affects INL, DNL, and TUE. A reference with a tight temperature
coefficient specification should be chosen to reduce temperature
dependence of the DAC output voltage in ambient conditions.
In high accuracy applications, which have a relatively low noise
budget, reference output voltage noise needs to be considered. It
is important to choose a reference with as low an output noise
voltage as practical for the system noise resolution required.
Precision voltage references such as the ADR425 produce low
output noise in the 0.1 Hz to 10 Hz range. Examples of recom-
mended precision references for use as supply to the AD5680
are shown in the Table 6.
0.1 Hz to 10 Hz Noise (μV p-p typ)
3.4
5
50
V
5
5
5
OUT
(V)
AD5680