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參數資料
| 型號： | AD9235 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | ADC |
| 英文描述： | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
| 中文描述： | 12位，20/40/65MSPS的3V A/D轉換器 |
| 文件頁數： | 16/32頁 |
| 文件大小： | 1181K |
| 代理商： | AD9235 |
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REV. B
AD9235
–16–
reference amplifier switch is connected to the internal resistor
divider (see Figure 12), setting VREF to 1 V. Connecting the
SENSE pin to VREF switches the reference amplifier output to
the SENSE pin, completing the loop and providing a 0.5 V
reference output. If a resistor divider is connected as shown in
Figure 13, the switch will again be set to the SENSE pin. This
will put the reference amplifier in a noninverting mode with the
VREF output defined as follows.
VREF
R
R
=
×
+
(
)
0 5
.
1
2
1
SENSE
ADC
CORE
SELECT
LOGIC
AD9235
VREF
VIN–
VIN+
REFB
REFT
0.1 F
10 F
0.1 F
10 F
0.1 F
0.1 F
0.5V
Figure 12. Internal Reference Configuration
In all reference configurations, REFT and REFB drive the A/D
conversion core and establish its input span. The input range of
the ADC always equals twice the voltage at the reference pin for
either an internal or an external reference.
SENSE
ADC
CORE
SELECT
LOGIC
AD9235
VREF
VIN–
VIN+
REFB
REFT
0.1 F
10 F
0.1 F
10 F
0.1 F
0.1 F
0.5V
R2
R1
Figure 13. Programmable Reference Configuration
External Reference Operation
The use of an external reference may be necessary to enhance the
gain accuracy of the ADC or improve thermal drift characteristics.
When multiple ADCs track one another, a single reference
(internal or external) may be necessary to reduce gain matching
errors to an acceptable level. A high precision external reference
may also be selected to provide lower gain and offset temperature
drift. Figure 14 shows the typical drift characteristics of the
internal reference in both 1 V and 0.5 V modes.
TEMPERATURE ( C)
V
1.2
–40 –30 –20 –10
0
10
20
30
40
50
60
70
80
1.0
0.8
0.6
0.4
0.0
0.2
VREF = 1.0V
VREF = 0.5V
Figure 14. Typical VREF Drift
When the SENSE pin is tied to AVDD, the internal reference
will be disabled, allowing the use of an external reference. An
internal reference buffer will load the external reference with an
equivalent 7 k
load. The internal buffer will still generate the
positive and negative full-scale references, REFT and REFB, for
the ADC core. The input span will always be twice the value of
the reference voltage; therefore, the external reference must be
limited to a maximum of 1 V.
If the internal reference of the AD9235 is used to drive multiple
converters to improve gain matching, the loading of the reference
by the other converters must be considered. Figure 15 depicts
how the internal reference voltage is affected by loading.
LOAD (mA)
E
0.05
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.00
–0.25
–0.20
–0.15
–0.10
–0.05
0.5V ERROR (%)
1V ERROR (%)
Figure 15. VREF Accuracy vs. Load
相關PDF資料 |
PDF描述 |
|---|---|
| AD9235BCP-20 | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
| AD9235BCP-40 | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
| AD9235BCP-65 | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
| AD9235BRU-20 | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
| AD9235BRU-40 | 12-Bit, 20/40/65 MSPS 3 V A/D Converter |
相關代理商/技術參數 |
參數描述 |
|---|---|
| AD9235-20PCB | 制造商:Analog Devices 功能描述:Development Tools, 12-Bit, 20/40/65MSPS 3V A/D Converter 制造商:Analog Devices 功能描述:DEV TOOLS, 12-BIT, 20/40/65MSPS 3V A/D CNVRTR - Bulk |
| AD9235-40PCB | 制造商:Analog Devices 功能描述:DEV TOOLS, 12-BIT, 20/40/65MSPS 3V A/D CNVRTR - Bulk |
| AD9235-65PCB | 制造商:Analog Devices 功能描述:Development Tools, 12-Bit, 20/40/65MSPS 3V A/D Converter 制造商:Analog Devices 功能描述:DEV TOOLS, 12-BIT, 20/40/65MSPS 3V A/D CNVRTR - Bulk |
| AD9235BCP-20 | 制造商:Analog Devices 功能描述:ADC Single Pipelined 20Msps 12-bit Parallel 32-Pin LFCSP EP 制造商:Analog Devices 功能描述:ADC SGL PIPELINED 20MSPS 12-BIT PARALLEL 32LFCSP EP - Bulk |
| AD9235BCP-20EB | 制造商:Analog Devices 功能描述:EVAL BD FOR 12-BIT, 20/40/65 MSPS ,3V A/D CNVRTR - Bulk |
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