AD5664 Analog Devices, AD5664 Datasheet - Page 20

• Manufacturer Part Number: AD5664
• Manufacturer: Analog Devices

Specifications of AD5664

• Resolution (bits): 16bit
• Dac Update Rate: 223kSPS
• Dac Settling Time: 4µs
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

AD5624/AD5664
APPLICATIONS
CHOOSING A REFERENCE FOR THE
AD5624/AD5664
To achieve the optimum performance from the AD5624/
AD5664, thought should be given to the choice of a precision
voltage reference. The AD5624/AD5664 have only one
reference input, V
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. Choosing a reference with an output trim
adjustment, such as the ADR423, 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.
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
output noise in the 0.1 Hz to10 Hz range. Examples of recom-
mended precision references for use as supply to the
AD5624/AD5664 are shown in the Table 14.
Table 14. Partial List of Precision References for Use with the AD5624/AD5664
Part No.
ADR425
ADR395
REF195
AD780
ADR423
Initial Accuracy (mV max)
±2
±6
±2
±2
±2
REF
. The voltage on the reference input is used
ADR425
produce low
Temp Drift (ppm
3
25
5
3
3
Rev. 0 | Page 20 of 24
o
C max)
USING A REFERENCE AS A POWER SUPPLY FOR
THE AD5624/AD5664
Because the supply current required by the AD5624/AD5664 is
extremely low, an alternative option is to use a voltage reference
to supply the required voltage to the part (see Figure 39). This is
especially useful if the power supply is quite noisy, or if the
system supply voltages are at some value other than 5 V or 3 V,
for example, 15 V. The voltage reference outputs a steady supply
voltage for the AD5624/AD5664 (see Table 14 for a suitable
reference). If the low dropout
450 μA of current to the AD5624/AD5664, with no load on the
output of the DAC. When the DAC output is loaded, the
REF195
current required (with a 5 kΩ load on the DAC output) is
The load regulation of the
which results in a 2.9 ppm (14.5 μV) error for the 1.45 mA
current drawn from it. This corresponds to a 0.191 LSB error.
INTERFACE
450 μA + (5 V/5 kΩ) = 1.45 mA
SERIAL
Figure 39. REF195 as Power Supply to the AD5624/AD5664
3-WIRE
also needs to supply the current to the load. The total
0.1 Hz to 10 Hz Noise (μV p-p typ)
3.4
5
50
4
3.4
SYNC
SCLK
DIN
15V
REF195
REF195
REF195
5V
AD5624/
AD5664
V
DD
is typically 2 ppm/mA,
V
is used, it must supply
REF
500mA
V
OUT
= 0V TO 5V
V
5
5
5
2.5/3
3
OUT
(V)