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參數資料
| 型號： | AD7651AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 16-Bit 100 kSPS PulSAR Unipolar ADC with Reference |
| 中文描述： | 1-CH 16-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL/PARALLEL ACCESS, PQFP48 |
| 封裝： | MS-026BBC, LQFP-48 |
| 文件頁數： | 25/28頁 |
| 文件大小： | 709K |
| 代理商： | AD7651AST |
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AD7651
APPLICATION HINTS
BIPOLAR AND WIDER INPUT RANGES
In some applications, it is desirable to use a bipolar or wider
analog input range such as ±10 V, ±5 V, or 0 V to 5 V. Although
the AD7651 has only one unipolar range, simple modifications
of input driver circuitry allow bipolar and wider input ranges to
be used without any performance degradation.
a connection diagram that allows this. Component values
required and resulting full-scale ranges are shown in
shows
.
Figure 38
Figure 38
Figure 38. Using the AD7651 in 16-Bit Bipolar and/or Wider Input Ranges
Table 8
Table 8. Component Values and Input Ranges
Input Range
R1 ()
±10 V
500
±5 V
500
0 V to –5 V
500
LAYOUT
The AD7651 has very good immunity to noise on the power
supplies. However, care should still be taken with regard to
grounding layout.
When desired, accurate gain and offset can be calibrated by
acquiring a ground and voltage reference using an analog
multiplexer (U2), as shown in
.
U1
ANALOG
INPUT
R2
R3
R4
100nF
R1
U2
C
REF
IN
INGND
REF
REFGND
AD7651
02964-0-022
C
F
R2 (k)
4
2
1
R3 (k)
2.5
2.5
None
R4 (k)
2
1.67
0
The printed circuit board that houses the AD7651 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 separated easily. Digital and analog
ground planes should be joined in only one place, preferably
underneath the AD7651, or as close as possible to the AD7651.
If the AD7651 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 that should
be established as close as possible to the AD7651.
Running digital lines under the device should be avoided since
these will couple noise onto the die. The analog ground plane
should be allowed to run under the AD7651 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 crosstalk
through the board.
The power supply lines to the AD7651 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 supply’s impedance presented to the
AD7651 and to reduce the magnitude of the supply spikes.
Decoupling ceramic capacitors, typically 100 nF, should be
placed on each power supply pin—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 near the ADC to further reduce
low frequency ripple.
The DVDD supply of the AD7651 can be a separate supply or
can come from the analog supply AVDD or the digital interface
supply OVDD. When the system digital supply is noisy or when
fast switching digital signals are present, if no separate supply is
available, the user should connect DVDD to AVDD through an
RC filter (see F
) and the system supply to 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.
igure 22
The AD7651 has five different ground pins: INGND, REFGND,
AGND, DGND, and OGND. INGND is used to sense the analog
input signal. REFGND senses the reference voltage and, because
it carries pulsed currents, should be a low impedance return to
the reference. AGND is the ground to which most internal ADC
analog signals are referenced; it 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.
EVALUATING THE AD7651’S PERFORMANCE
A recommended layout for the AD7651 is outlined in the
EVAL-AD7651
evaluation board for the AD7651. 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 BRD2
.
Rev. 0 | Page 25 of 28
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| AD7651ASTZ | 功能描述:IC ADC 16BIT 100KSPS 48-LQFP RoHS:是 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:PulSAR® 標準包裝:1 系列:microPOWER™ 位數:8 采樣率（每秒）:1M 數據接口:串行，SPI? 轉換器數目:1 功率耗散（最大）:- 電壓電源:模擬和數字 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應商設備封裝:24-VQFN 裸露焊盤（4x4） 包裝:Digi-Reel® 輸入數目和類型:8 個單端，單極 產品目錄頁面:892 (CN2011-ZH PDF) 其它名稱:296-25851-6 |
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