EVAL-AD5570EBZ Analog Devices Inc, EVAL-AD5570EBZ Datasheet - Page 19

• Manufacturer Part Number: EVAL-AD5570EBZ
• Description: 206-10G-01 Board I.c.
• Manufacturer: Analog Devices Inc
• Series: 0040r

Specifications of EVAL-AD5570EBZ

• Number Of Dac's: *
• Number Of Bits: 16
• Outputs And Type: 1, Single Ended
• Sampling Rate (per Second): 83k
• Data Interface: Serial
• Settling Time: 12µs
• Dac Type: *
• Voltage Supply Source: Dual ±
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD5570
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
TYPICAL OPERATING CIRCUIT
Figure 39 shows the typical operating circuit for the AD5570.
The only external component needed for this precision 16-bit
DAC is a single external positive reference. Because the device
incorporates reference buffers, it eliminates the need for a negative
reference, external inverters, precision amplifiers, and resistors.
This leads to an overall savings of both cost and board space.
In the circuit shown in Figure 39, V
to ±15 V, but V
16.5 V. AGNDS is connected to AGND, but the option of force/
sense is included on this device if required by the user.
–15V
+15V
Force/Sense of AGND
Because of the extremely high accuracy of this device, system
design issues (such as grounding and contact resistance) are
very important. The AD5570, with ±10 V output, has an LSB
size of 305 μV. Therefore, series wiring and connector resistances
of very small values can cause voltage drops of an LSB. For this
reason, the AD5570 offers a force/sense output configuration.
Figure 40 shows how to connect the AD5570 to the force/sense
amplifier. Where accuracy of the output is important, an ampli-
fier such as the OP177 is ideal. The OP177 is ultraprecise with
offset voltages of 10 μV maximum at room temperature, and off-
set drift of 0.1 μV/°C maximum. Alternative recommended
amplifiers are the OP1177 and the OP77. For applications where
optimization of the circuit for settling time is needed, the AD845
is recommended.
Precision Voltage Reference Selection
To achieve the optimum performance from the AD5570, give
special attention to the selection of a precision voltage reference.
The AD5570 has just one reference input, REFIN. This voltage
on REFIN is used to provide a buffered positive and negative
reference for the DAC core. Therefore, any error in the voltage
reference is reflected in the output of the device.
0.1µF
0.1µF
10µF
10µF
LDAC
SYNC
SCLK
SDIN
SDO
DD
Figure 39. Typical Operating Circuit
and V
5kΩ
1
2
3
4
5
6
7
8
SS
V
V
CLR
LDAC
SYNC
SCLK
SDIN
SDO
can operate supplies from 11.4 V to
SS
DD
AD5570
DD
and V
REFGND
REFGND
AGNDS
REFIN
AGND
DGND
V
OUT
PD
SS
are both connected
16
15
14
13
12
11
10
9
5V
ADR435
V
OUT
Rev. C | Page 19 of 24
The four possible sources of error to consider when choosing
a voltage reference for high accuracy applications are initial
accuracy, long-term drift, temperature coefficient of the out-
put voltage, and output voltage noise.
Initial accuracy on the output voltage of an external reference can
lead to a full-scale error in the DAC. Therefore, to minimize
these errors, a reference with low initial accuracy specification
is preferred. Also, choosing a reference with an output trim adjust-
ment, such as the ADR425, allows a system designer to trim out
system errors by setting the reference voltage to a voltage other
than the nominal. The trim adjustment can also be used at tem-
perature to trim out any error.
Long-term drift (LTD) is a measure of how much the reference
drifts over time. A reference with a tight long-term drift specifica-
tion ensures that the overall solution remains relatively stable
over its entire lifetime.
The temperature coefficient of a references output voltage
affects INL, DNL, and TUE. Choose a reference with a tight
temperature coefficient specification to reduce the depend
ence of the DAC output voltage on ambient conditions.
In high accuracy applications that 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 resolution required. Precision
voltage references, such as the ADR435 (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
can be required to minimize the output noise.
Figure 40. Driving AGND and AGNDS Using a Force/Sense Amplifier
*FOR OPTIMUM SETTLING TIME PERFORMANCE,
THE AD845 IS RECOMMENDED.
(OTHER CONNECTIONS OMITTED
1
2
3
4
5
6
7
8
V
V
CLR
LDAC
SYNC
SCLK
SDIN
SDO
SS
DD
FOR CLARITY)
AD5570
REFGND
REFGND
AGNDS
REFIN
AGND
DGND
V
OUT
PD
16
15
14
13
12
11
10
9
OP177*
6
2
3
AD5570