AD9480(Rev0) 查看數據表（PDF） - Analog Devices
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AD9480 Datasheet PDF : 28 Pages
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The AD9480 can be easily configured for different full-scale
ranges. See the Voltage Reference section for more information.
Optimal performance is achieved with a 1 V p-p analog input.
SENSE = GND
VIN+
500mV 2.0V
VIN–
DIGITALOUT = ALL 1s
2.0V
DIGITALOUT = ALL 0s
Figure 13. Analog Input Full Scale
VOLTAGE REFERENCE
A stable and accurate 1.0 V reference is built into the AD9480.
Users can choose this internal reference or provide an external
reference for greater accuracy and flexibility. Figure 15 shows
the typical reference variation with temperature. Table 9
summarizes the available reference configurations.
VIN+
VIN–
ADC
CORE
VREF
+
10µF 0.1µF
SENSE
7kΩ
SELECT
LOGIC
AD9480
Fixed Reference
The internal reference can be configured for a differential span
of 1 V p-p (see Figure 17). It is recommended to place a 0.1uF
capacitor as close as possible to the VREF pin; a 10 uF capacitor
is also required (see the PCB layout for guidance). If the internal
reference of the AD9480 is used to drive multiple converters to
improve gain matching, the loading of the reference by the
other converters must be considered. Figure 17 depicts how the
internal reference voltage is affected by loading.
1.0085
1.0080
1.0075
1.0070
1.0065
1.0060
1.0055
1.0050
1.0045
1.0040
1.0035
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
Figure 15. Typical Reference Variation with Temperature
10µF 0.1µF
VREF
SENSE
Figure 16. Internal Fixed Reference (1 V p-p)
0
–0.1
7kΩ
0.5V
–0.2
–0.3
Figure 14. Internal Reference Equivalent Circuit
–0.4
–0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
IREF (mA)
Figure 17. Internal VREF vs. Load Current
Table 9. Reference Configurations
SENSE Voltage
Resulting VREF
AVDD
N/A (external reference input)
0.5 V (Self Biased)
0.5 × (1 + R1/R2) V
AGND to 0.2 V
1.0 V
Reference
External
Programmable
Internal fixed
Differential Span
1 x external reference voltage
1 × VREF (0.75 V p-p to 1.5 V p-p)
1 V p-p
Rev. 0 | Page 13 of 28
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