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參數(shù)資料
| 型號： | MAX1191 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | ADC |
| 英文描述： | Ultra-Low-Power, 7.5Msps, Dual 8-Bit ADC |
| 中文描述： | 超低功耗、7.5Msps、雙路、8位ADC |
| 文件頁數(shù)： | 23/27頁 |
| 文件大?。?/td> | 492K |
| 代理商： | MAX1191 |
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Ultra-Low-Power, 7.5Msps, Dual 8-Bit ADC
______________________________________________________________________________________
23
Typical QAM Demodulation Application
Quadrature amplitude modulation (QAM) is frequently
used in digital communications. Typically found in
spread-spectrum-based systems, a QAM signal repre-
sents a carrier frequency modulated in both amplitude
and phase. At the transmitter, modulating the baseband
signal with quadrature outputs, a local oscillator fol-
lowed by subsequent upconversion can generate the
QAM signal. The result is an in-phase (I) and a quadra-
ture (Q) carrier component, where the Q component is
90
°
phase shifted with respect to the in-phase compo-
nent. At the receiver, the QAM signal is demodulated
into analog I and Q components. Figure 12 displays the
demodulation process performed in the analog domain
using the MAX1191 dual-matched, 3V, 8-bit ADC and
the MAX2451 quadrature demodulator to recover and
digitize the I and Q baseband signals. Before being dig-
itized by the MAX1191, the mixed-down signal compo-
nents can be filtered by matched analog filters, such as
Nyquist or pulse-shaping filters. The filters remove
unwanted images from the mixing process, thereby
enhancing the overall signal-to-noise (SNR) perfor-
mance and minimizing intersymbol interference.
Grounding, Bypassing,
and Board Layout
The MAX1191 requires high-speed board layout design
techniques. Refer to the MAX1193 Evaluation Kit data
sheet for a board layout reference. Locate all bypass
capacitors as close to the device as possible, prefer-
ably on the same side as the ADC, using surface-
mount devices for minimum inductance. Bypass V
DD
to
GND with a 0.1μF ceramic capacitor in parallel with a
2.2μF bipolar capacitor. Bypass OV
DD
to OGND with a
0.1μF ceramic capacitor in parallel with a 2.2μF bipolar
capacitor. Bypass REFP, REFN, and COM each to
GND with a 0.33μF ceramic capacitor.
Multilayer boards with separated ground and power
planes produce the highest level of signal integrity. Use
a split ground plane arranged to match the physical
location of the analog ground (GND) and the digital
output driver ground (OGND) on the ADC
’
s package.
Connect the MAX1191 exposed backside paddle to
GND. Join the two ground planes at a single point such
that the noisy digital ground currents do not interfere
with the analog ground plane. The ideal location of this
connection can be determined experimentally at a
point along the gap between the two ground planes,
which produces optimum results. Make this connection
with a low-value, surface-mount resistor (1
to 5
), a
ferrite bead, or a direct short. Alternatively, all ground
pins could share the same ground plane, if the ground
plane is sufficiently isolated from any noisy, digital sys-
tems ground plane (e.g., downstream output buffer or
DSP ground plane).
Route high-speed digital signal traces away from the
sensitive analog traces of either channel. Make sure to
isolate the analog input lines to each respective con-
verter to minimize channel-to-channel crosstalk. Keep
all signal lines short and free of 90
°
turns.
0
°
90
°
÷
8
DOWNCONVERTER
MAX2451
INA+
INA-
MAX1191
INB+
INB-
DSP
POST-
PROCESSING
A/B
Figure 12. Typical QAM Receiver Application
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PDF描述 |
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| MAX1198ECM | Dual, 8-Bit, 100Msps, 3.3V, Low-Power ADC with Internal Reference and Parallel Outputs |
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1191ETI | 功能描述:模數(shù)轉換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX1191ETI+ | 功能描述:模數(shù)轉換器 - ADC 8-Bit 2Ch 7.5Msps 3.6V Precision ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX1191ETI+T | 功能描述:模數(shù)轉換器 - ADC 8-Bit 2Ch 7.5Msps 3.6V Precision ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX1191ETI-T | 功能描述:模數(shù)轉換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX1192ETI | 功能描述:模數(shù)轉換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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