AD5662BRJZ-2500RL7 Analog Devices Inc, AD5662BRJZ-2500RL7 Datasheet - Page 18

• Manufacturer Part Number: AD5662BRJZ-2500RL7
• Description: Single 16bit SPI DAC Reset To Midscale
• Manufacturer: Analog Devices Inc
• Series: nanoDAC™r

Specifications of AD5662BRJZ-2500RL7

• Design Resources: 4 mA to 20 mA Process Control Loop Using AD5662 (CN0009) 16-Bit Fully Isolated Voltage Output Module Using AD5662, ADuM1401, and External Amplifiers (CN0063) 16-Bit Fully Isolated 4 mA to 20 mA Output Module Using AD5662, ADuM1401, and External Amplifiers (CN0064)
• Settling Time: 8µs
• Number Of Bits: 16
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 750µW
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5662
APPLICATIONS
CHOOSING A REFERENCE FOR THE AD5662
To achieve the optimum performance from the AD5662,
thought should be given to the choice of a precision voltage
reference. The AD5662 has only one reference input, V
voltage on the reference 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 ADR423, allows a system designer
to trim system errors out 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
effect 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 to10 Hz range. Examples of recom-
mended precision references for use as supply to the AD5662
are shown in the Table 6.
Table 6. Partial List of Precision References for Use with the AD5662
Part No.
ADR425
ADR395
REF195
AD780
ADR423
Initial Accuracy (mV max)
±2
±6
±2
±2
±2
Temp Drift (ppm
3
25
5
3
3
REF
. The
Rev. A | Page 18 of 24
o
C max)
USING A REFERENCE AS A
POWER SUPPLY FOR THE AD5662
Because the supply current required by the AD5662 is extremely
low, an alternative option is to use a voltage reference to supply
the required voltage to the part (see Figure 41). 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 AD5662; see Table 6 for a suitable reference. If the low drop-
out REF195 is used, it must supply 250 μA of current to the
AD5662, with no load on the output of the DAC. When the
DAC output is loaded, the REF195 also needs to supply the
current to the load. The total current required (with a 5 kΩ
load on the DAC output) is
The load regulation of the REF195 is typically 2 ppm/mA,
which results in a 2.5 ppm (12.5 μV) error for the 1.25 mA
current drawn from it. This corresponds to a 0.164 LSB error.
INTERFACE
250 μA + (5 V/5 kΩ) = 1.25 mA
SERIAL
3-WIRE
0.1 Hz to 10 Hz Noise (μV p-p typ)
3.4
5
50
4
3.4
Figure 41. REF195 as Power Supply to the AD5662
+15V
SYNC
SCLK
DIN
REF195
+5V
V
DD
AD5662
V
REF
250 μ A
V
OUT
= 0V TO 5V
V
5
5
5
2.5/3
3
OUT
(V)