参数资料
| 型号： | AD9267BCPZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 5/24页 |
| 文件大小： | 0K |
| 描述： | IC MOD SIGMA-DELTA DUAL 64LFCSP |
| 标准包装： | 1 |
| 类型： | 三角积分调制器 |
| 应用： | 无线通信系统 |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 64-VFQFN 裸露焊盘，CSP |
| 供应商设备封装： | 64-LFCSP-VQ（9x9） |
| 包装： | 托盘 |
AD9267
Rev. 0 | Page 13 of 24
THEORY OF OPERATION
The AD9267 uses a continuous time Σ-Δ modulator to convert
the analog input to a digital word. The modulator consists of a
continuous time loop filter preceding a quantizer (see Figure 27),
which samples at fMOD = 640 MSPS. This produces an oversam-
pling ratio (OSR) of 32 for a 10 MHz input bandwidth. The output
of the quantizer is fed back to a DAC that ideally cancels the
input signal. The incomplete input cancellation residue is filtered
by the loop filter and is used to form the next quantizer sample.
H(f)
LOOP FILTER
QUANTIZER
+
–
DAC
ADC
MODULATOR
07
77
3-
02
1
Figure 27. Σ-Δ Modulator Overview
The quantizer produces a nine-level digital word. The quantiza-
tion noise is spread uniformly over the Nyquist band (see
Figure 28) but the feedback loop causes the quantization noise
present in the nine-level output to have a nonuniform spectral
shape. This noise shaping technique (see Figure 29) pushes the
in-band noise out of band; therefore, the amount of quantiza-
tion noise in the frequency band of interest is minimal.
QUANTIZATION NOISE
fMOD/2
BAND OF INTEREST
07
77
3-
0
22
Figure 28. Quantization Noise
NOISE SHAPING
BAND OF INTEREST
fMOD/2
0
77
73
-02
3
Figure 29. Noise Shaping
ANALOG INPUT CONSIDERATIONS
The continuous time modulator removes the need for an anti-
alias filter at the input to the AD9267. A discrete time converter
aliases signals around the sample clock frequency and its
multiples to the band of interest (see Figure 30). An external
antialias filter is needed to reject these signals.
DESIRED
INPUT
UNDESIRED
SIGNAL
ADC
fS
fS/2
07
77
3-
02
4
Figure 30. Discrete Time Converter
In contrast, the continuous time Σ-Δ modulator used within the
AD9267 has inherent antialiasing. The antialiasing property
results from sampling occurring at the output of the loop filter
(see Figure 31), and thus aliasing occurs at the same point in the
loop as quantization noise is injected; aliases are shaped by the
same mechanism as quantization noise. The quantization noise
transfer function, NTF(f), has zeros in the band of interest and
in all alias bands because NTF(f) is a discrete time transfer
function, whereas the loop filter transfer function, LF(f),
introduces poles only in the band of interest because LF(f) is a
continuous time transfer function. The signal transfer function,
being the product of NTF(f) and LF(f), only has zeros in all
alias bands and therefore suppresses all aliases.
LF(f)
H(z)
QUANTIZATION
NOISE
INP UT
OUTPUT
LOOP FILTER
fMOD
f
NTF(f)
L F (f)
07
77
3-
0
25
Figure 31. Continuous Time Converter
Input Common Mode
The analog inputs of the AD9267 are not internally dc biased.
In ac-coupled applications, the user must provide this bias
externally. Setting the device such that VCM = AVDD is
recommended for optimum performance. The analog inputs
are 500 Ω resistors and the internal reference loop aims to
develop 0.5 V across each input resistor (see Figure 32). With
0 V differential input, the driver sources 1 mA into each
analog input.
TO LOOP FILTER
STAGE 2
DAC
AVDD – 0.5V
500
500
VIN+x
VIN–x
FROM QUANTIZER
0
7773-
026
2.3V
1.8V
1.3V
2.3V
1.8V
1.3V
Figure 32. Input Common Mode
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD9267BCPZRL7 | 功能描述:IC MOD SIGMA-DELTA DUAL 64LFCSP RoHS:是 类别:集成电路 (IC) >> 专用 IC 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:调帧器 应用:数据传输 安装类型:表面贴装 封装/外壳:400-BBGA 供应商设备封装:400-PBGA（27x27） 包装:散装 |
| AD9267EBZ | 功能描述:BOARD EVALUATION FOR AD9267 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 |
| AD9268 | 制造商:AD 制造商全称:Analog Devices 功能描述:16-Bit, 80 MSPS/105 MSPS/125 MSPS, 1.8 V Dual Analog-to-Digital Converter (ADC) |
| AD9268-105EBZ1 | 制造商:AD 制造商全称:Analog Devices 功能描述:16-Bit, 80 MSPS/105 MSPS/125 MSPS, 1.8 V Dual Analog-to-Digital Converter (ADC) |
| AD9268-125EBZ | 功能描述:数据转换 IC 开发工具 Dual 16 bit 125 high SNR ADC RoHS:否 制造商:Texas Instruments 产品:Demonstration Kits 类型:ADC 工具用于评估:ADS130E08 接口类型:SPI 工作电源电压:- 6 V to + 6 V |
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