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參數資料
| 型號： | AD7641 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 18-Bit, 2 MSPS SAR ADC |
| 中文描述： | 18位，2 MSPS的SAR型ADC |
| 文件頁數： | 22/24頁 |
| 文件大?。?/td> | 324K |
| 代理商： | AD7641 |
AD7641
Preliminary Technical Data
APPLICATION HINTS
LAYOUT
The AD7641 has very good immunity to noise on the power
supplies. However, care should still be taken with regard to
grounding layout.
Rev. Pr E | Page 22 of 24
The printed circuit board that houses the AD7641 should be
designed so the analog and digital sections are separated and
confined to certain areas of the board. This facilitates the use of
ground planes that can be easily separated. Digital and analog
ground planes should be joined in only one place, preferably
underneath the AD7641, or, at least, as close as possible to the
AD7641. If the AD7641 is in a system where multiple devices
require analog to digital ground connections, the connection
should still be made at one point only, a star ground point,
which should be established as close as possible to the AD7641.
It is recommended to avoid running digital lines under the
device as these will couple noise onto the die. The analog
ground plane should be allowed to run under the AD7641 to
avoid noise coupling. Fast switching signals like CNVST or
clocks should be shielded with digital ground to avoid radiating
noise to other sections of the board, and should never run near
analog signal paths. Crossover of digital and analog signals
should be avoided. Traces on different but close layers of the
board should run at right angles to each other. This will reduce
the effect of feedthrough through the board. The power supply
lines to the AD7641 should use as large a trace as possible to
provide low impedance paths and reduce the effect of glitches
on the power supply lines. Good decoupling is also important to
lower the supplies impedance presented to the AD7641 and
reduce the magnitude of the supply spikes. Decoupling ceramic
capacitors, typically 100 nF, should be placed on each power
supplies pins AVDD, DVDD and OVDD close to, and ideally
right up against these pins and their corresponding ground
pins. Additionally, low ESR 10 μF capacitors should be located
in the vicinity of the ADC to further reduce low frequency
ripple.
The DVDD supply of the AD7641 can be either a separate
supply or come from the analog supply, AVDD, or from the
digital interface supply, OVDD. When the system digital supply
is noisy, or fast switching digital signals are present, it is
recommended if no separate supply is available, to connect the
DVDD digital supply to the analog supply AVDD through an
RC filter as shown in Figure 7, and connect the system supply to
the interface digital supply OVDD and the remaining digital
circuitry. When DVDD is powered from the system supply, it is
useful to insert a bead to further reduce high-frequency spikes.
The AD7641 has four different ground pins; REFGND, AGND,
DGND, and OGND. REFGND senses the reference voltage and
should be a low impedance return to the reference because it
carries pulsed currents. AGND is the ground to which most
internal ADC analog signals are referenced. This ground must
be connected with the least resistance to the analog ground
plane. DGND must be tied to the analog or digital ground plane
depending on the configuration. OGND is connected to the
digital system ground.
The layout of the decoupling of the reference voltage is
important. The decoupling capacitor should be close to the
ADC and connected with short and large traces to minimize
parasitic inductances.
EVALUATING THE AD7641 PERFORMANCE
A recommended layout for the AD7641 is outlined in the
documentation of the EVAL-AD7641-CB, evaluation board for
the AD7641. The evaluation board package includes a fully
assembled and tested evaluation board, documentation, and
software for controlling the board from a PC via the Eval-
Control BRD3.
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| AD7641BCPZ | 功能描述:IC ADC 18BIT 2MSPS SAR 48-LFCSP RoHS:是 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 其它有關文件:TSA1204 View All Specifications 標準包裝:1 系列:- 位數:12 采樣率（每秒）:20M 數據接口:并聯 轉換器數目:2 功率耗散（最大）:155mW 電壓電源:模擬和數字 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-TQFP 供應商設備封裝:48-TQFP（7x7） 包裝:Digi-Reel® 輸入數目和類型:4 個單端，單極；2 個差分，單極 產品目錄頁面:1156 (CN2011-ZH PDF) 其它名稱:497-5435-6 |
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