AD5934
Rev. A | Page 32 of 40
CHOOSING A REFERENCE FOR THE AD5934
To achieve the best performance from the AD5934, carefully
choose the precision voltage reference. The AD5934 has three
reference inputs: AVDD1, AVDD2, and DVDD. The voltage on
these reference inputs should be run from the same voltage supply.
There are four possible sources of error that should be considered
when choosing a voltage reference for high accuracy applications:
initial accuracy, ppm drift, long term drift, and output voltage
noise. To minimize these errors, a reference with high initial
accuracy is preferred. In addition, choosing a reference with an
output trim adjustment, such as a device in the ADR43x family,
allows a system designer to trim 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.
Because the supply current required by the AD5934 is extremely
low, the parts are ideal for low supply applications. The
voltage reference is recommended in this case. The
requires less than 100 μA of quiescent current. It also provides
good noise performance at 8 μV p-p in the 0.1 Hz to 10 Hz range.
Long-term drift is a measure of how much the reference drifts
over time. A reference with a tight long term drift specification
ensures that the overall solution remains stable during its lifetime.
A reference with a tight temperature coefficient specification
should be chosen to reduce the temperature dependence of the
system 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 noise resolution required is important.
Precision voltage references, such as the
, produce low
output noise in the 0.1 Hz to 10 Hz range. Examples of some
recommended precision references for use as supply to the
AD5934 are shown in Table 17.
Table 17. List of Precision References for the AD5934
Part No.
Initial Accuracy (mV max)
Output Voltage (V)
Temperature Drift (ppm/°C max)
0.1 Hz to 10 Hz Noise (μV p-p typ)
±1.5 3.0
3
3.75
±4
3.0
10
3.75
±1.5 4.096
3
6.25
±5 4.096
10
6.25
±2 5.0
3
8
±6 5.0
10
8
±2 4.5
3
7.5
±5.5 4.5
10
7.5
Содержание AD5934
Страница 35: ...AD5934 Rev A Page 35 of 40 SCHEMATICS 05325 144 Figure 40 EVAL AD5934EBZ USB Schematic ...
Страница 36: ...AD5934 Rev A Page 36 of 40 05325 145 Figure 41 EVAL AD5934EBZ Schematic ...
Страница 37: ...AD5934 Rev A Page 37 of 40 05325 146 Figure 42 Linear Regulator on EVAL AD5934EBZ ...
Страница 38: ...AD5934 Rev A Page 38 of 40 05325 147 Figure 43 Decoupling on the EVAL AD5934EBZ ...