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| 型号： | AD9643BCPZ-250 |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | ADC |
| 英文描述： | 2-CH 14-BIT FLASH METHOD ADC, PARALLEL ACCESS, QCC64 |
| 封装： | 9 X 9 MM, ROHS COMPLIANT, MO-220VMMD-4, LFCSP-64 |
| 文件页数： | 17/36页 |
| 文件大小： | 1659K |
| 代理商： | AD9643BCPZ-250 |
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AD9643
Rev. A | Page 24 of 36
differential drivers provide excellent performance and a flexible
interface to the ADC.
The output common-mode voltage of the ADA4930-2 is easily
set with the VCM pin of the AD9643 (see Figure 47), and the
driver can be configured in a Sallen-Key filter topology to
provide band-limiting of the input signal.
VIN
76.8
120
0.1F
200
90
0.1F
AVDD
33
15
5pF
15pF
ADC
VIN–
VIN+
VCM
ADA4930-2
09
63
6-
0
51
Figure 47. Differential Input Configuration Using the ADA4930-2
For baseband applications where SNR is a key parameter,
differential transformer coupling is the recommended input
configuration. An example is shown in Figure 48. To bias the
analog input, the VCM voltage can be connected to the center
tap of the secondary winding of the transformer.
2V p-p
49.9
0.1F
R1
C1
ADC
VIN+
VIN–
VCM
C2
R2
R3
R2
C2
09
63
6-
05
2
R3
0.1F
33
Figure 48. Differential Transformer-Coupled Configuration
The signal characteristics must be considered when selecting
a transformer. Most RF transformers saturate at frequencies
below a few megahertz. Excessive signal power can also cause
core saturation, which leads to distortion.
At input frequencies in the second Nyquist zone and above, the
noise performance of most amplifiers is not adequate to achieve
the true SNR performance of the AD9643. For applications where
SNR is a key parameter, differential double balun coupling is
the recommended input configuration (see Figure 50). In this
configuration, the input is ac-coupled and the VCM voltage is
provided to each input through a 33 Ω resistor. These resistors
compensate for losses in the input baluns to provide a 50 Ω
impedance to the driver.
In the double balun and transformer configurations, the value of
the input capacitors and resistors is dependent on the input fre-
quency and source impedance. Based on these parameters, the
value of the input resistors and capacitors may need to be adjusted
or some components may need to be removed. Table 10 displays
recommended values to set the RC network for different input
frequency ranges. However, these values are dependent on the
input signal and bandwidth and should be used only as a
starting guide. Note that the values given in Table 10 are for each
Table 10. Example RC Network
Frequency
Range
(MHz)
R1
Series
(Ω)
C1
Differential
(pF)
R2
Series
(Ω)
C2
Shunt
(pF)
R3
Shunt
(Ω)
0 to 100
33
8.2
0
15
49.9
100 to 300
15
3.9
0
8.2
49.9
An alternative to using a transformer-coupled input at frequencies
in the second Nyquist zone is to use an amplifier with variable
(DVGAs) provides good performance for driving the AD9643.
Figure 49 shows an example of the AD8376 driving the AD9643
through a band-pass antialiasing filter.
AD8376
AD9643
1H
1nF
VPOS
VCM
15pF
68nH
2.5k║2pF
301
165
5.1pF
3.9pF
180nH
1000pF
NOTES
1. ALL INDUCTORS ARE COILCRAFT 0603CS COMPONENTS WITH THE
EXCEPTION OF THE 1H CHOKE INDUCTORS (COIL CRAFT 0603LS).
2. FILTER VALUES SHOWN ARE FOR A 20MHz BANDWIDTH FILTER
CENTERED AT 140MHz.
180nH
220nH
096
36-
05
4
Figure 49. Differential Input Configuration Using the AD8376
ADC
R1
0.1F
2V p-p
VIN+
VIN–
VCM
C1
C2
R1
R2
0.1F
S
0.1F
C2
33
S
PA
P
09
63
6-
0
53
R3
0.1F
33
Figure 50. Differential Double Balun Input Configuration
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相关代理商/技术参数 |
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| AD9643BCPZRL7-170 | 功能描述:模数转换器 - ADC 14 Bit 170Msps Dual ADC RoHS:否 制造商:Analog Devices 通道数量: 结构: 转换速率: 分辨率: 输入类型: 信噪比: 接口类型: 工作电源电压: 最大工作温度: 安装风格: 封装 / 箱体: |
| AD9643BCPZRL7-210 | 功能描述:模数转换器 - ADC 14 Bit 210Msps Dual ADC RoHS:否 制造商:Analog Devices 通道数量: 结构: 转换速率: 分辨率: 输入类型: 信噪比: 接口类型: 工作电源电压: 最大工作温度: 安装风格: 封装 / 箱体: |
| AD9643BCPZRL7-250 | 功能描述:模数转换器 - ADC 14 Bit 250Msps Dual ADC RoHS:否 制造商:Analog Devices 通道数量: 结构: 转换速率: 分辨率: 输入类型: 信噪比: 接口类型: 工作电源电压: 最大工作温度: 安装风格: 封装 / 箱体: |
| AD9644-155KITZ | 功能描述:KIT EVAL FOR AD9644 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
| AD9644-80KITZ | 功能描述:BOARD EVALUATION FOR AD9644 RoHS:是 类别:编程器，开发系统 >> 评估板 - 模数转换器 (ADC) 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- ADC 的数量:1 位数:12 采样率（每秒）:94.4k 数据接口:USB 输入范围:±VREF/2 在以下条件下的电源（标准）:- 工作温度:-40°C ~ 85°C 已用 IC / 零件:MAX11645 已供物品:板，软件 |
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