参数资料
型号: AD7266BSUZ
厂商: Analog Devices Inc
文件页数: 9/29页
文件大小: 0K
描述: IC ADC 12BIT 3CH 2MSPS 32-TQFP
设计资源: AD7266 SAR ADC in DC-Coupled Differential and Single-Ended Appls (CN0039)
标准包装: 1
位数: 12
采样率(每秒): 2M
数据接口: DSP,MICROWIRE?,QSPI?,串行,SPI?
转换器数目: 2
功率耗散(最大): 33.6mW
电压电源: 模拟和数字
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 32-TQFP
供应商设备封装: 32-TQFP(7x7)
包装: 托盘
输入数目和类型: 12 个单端,单极;6 个差分,单极;6 个伪差分,单极
产品目录页面: 777 (CN2011-ZH PDF)
AD7266
Rev. B | Page 16 of 28
Using an Op Amp Pair
An op amp pair can be used to directly couple a differential
signal to one of the analog input pairs of the AD7266. The
circuit configurations illustrated in Figure 26 and Figure 27
show how a dual op amp can be used to convert a single-ended
signal into a differential signal for both a bipolar and unipolar
input signal, respectively.
The voltage applied to Point A sets up the common-mode
voltage. In both diagrams, it is connected in some way to the
reference, but any value in the common-mode range can be
input here to set up the common mode. The AD8022 is a
suitable dual op amp that can be used in this configuration to
provide differential drive to the AD7266.
Take care when choosing the op amp; the selection depends on
the required power supply and system performance objectives.
The driver circuits in Figure 26 and Figure 27 are optimized for
dc coupling applications requiring best distortion performance.
The circuit configuration shown in Figure 26 converts a
unipolar, single-ended signal into a differential signal.
The differential op amp driver circuit shown in Figure 27 is
configured to convert and level shift a single-ended, ground-
referenced (bipolar) signal to a differential signal centered at the
VREF level of the ADC.
GND
2 × VREF p-p
27
V+
V–
V+
V–
VREF
2.5V
3.75V
1.25V
2.5V
3.75V
1.25V
DCAPA/DCAPB
VIN+
AD72661
VIN–
440
220
0.47F
1ADDITIONAL PINS OMITTED FOR CLARITY.
220
10k
A
04603
-023
Figure 26. Dual Op Amp Circuit to Convert a Single-Ended Unipolar Signal
into a Differential Signal
20k
220k
2 × VREF p-p
27
V+
V–
V+
V–
GND
2.5V
3.75V
1.25V
2.5V
3.75V
1.25V
DCAPA/DCAPB
VIN+
AD72661
VIN–
440
220
0.47F
1ADDITIONAL PINS OMITTED FOR CLARITY.
220
10k
A
046
03-
024
Figure 27. Dual Op Amp Circuit to Convert a Single-Ended Bipolar Signal
into a Differential Unipolar Signal
Pseudo Differential Mode
The AD7266 can have a total of six pseudo differential pairs. In
this mode, VIN+ is connected to the signal source that must have
an amplitude of VREF (or 2 × VREF, depending on the range
chosen) to make use of the full dynamic range of the part. A dc
input is applied to the VIN pin. The voltage applied to this input
provides an offset from ground or a pseudo ground for the VIN+
input. The benefit of pseudo differential inputs is that they
separate the analog input signal ground from the ADC’s ground
allowing dc common-mode voltages to be cancelled. The typical
voltage range for the VIN pin, while in pseudo differential
mode, is shown in Figure 28 and Figure 29. Figure 30 shows a
connection diagram for pseudo differential mode.
04603-043
VREF (V)
3.0
0
0.5
1.0
1.5
2.0
2.5
V
IN–
(V
)
1.0
0.8
0.4
0.6
0.2
–0.2
0
–0.4
TA = 25°C
Figure 28. VIN- Input Voltage Range vs. VREF in
Pseudo Differential Mode with VDD = 3 V
0
460
3-
04
4
VREF (V)
5.0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
V
IN
(V
)
2.5
2.0
1.5
1.0
0.5
0
–0.5
TA = 25°C
Figure 29. VIN Input Voltage Range vs. VREF in
Pseudo Differential Mode with VDD = 5 V
DC INPUT
VOLTAGE
VREF
p–p
VREF
VIN+
AD72661
VIN–
0.47F
1ADDITIONAL PINS OMITTED FOR CLARITY.
04
60
3-
0
25
Figure 30. Pseudo Differential Mode Connection Diagram
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