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參數資料
| 型號： | AD7676AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 16-Bit +-1 LSB INL, 500 kSPS, Differential ADC |
| 中文描述： | 1-CH 16-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL/PARALLEL ACCESS, PQFP48 |
| 封裝： | 1.40 MM HEIGHT, PLASTIC, MS-026BBC, LQFP-48 |
| 文件頁數： | 18/20頁 |
| 文件大小： | 321K |
| 代理商： | AD7676AST |
REV. 0
AD7676
–
18
–
AD7676
*
MC68HC11
*
SER/
PAR
EXT/
INT
CS
RD
IRQ
MISO/SDI
SCK
I/O PORT
BUSY
SDOUT
SCLK
CNVST
INVSCLK
DVDD
*
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 22. Interfacing the AD7676 to SPI Interface
ADSP-21065L in Master Serial Interface
As shown in Figure 23, the AD7676 can be interfaced to the
ADSP-21065L using the serial interface in master mode without any
glue logic required. This mode combines the advantages of reducing
the wire connections and the ability to read the data during or after
conversion maximum speed transfer (DIVSCLK[0:1] both low).
The AD7676 is configured for the internal clock mode (EXT/
INT low) and acts, therefore, as the master device. The convert
command can be generated by either an external low jitter oscil-
lator or, as shown, by a FLAG output of the ADSP-21065L or
by a frame output TFS of one serial port of the ADSP-21065L
which can be used like a timer. The serial port on the
ADSP-21065L is configured for external clock (IRFS = 0),
rising edge active (CKRE = 1), external late framed sync signals
(IRFS = 0, LAFS = 1, RFSR = 1) and active high (LRFS = 0).
The serial port of the ADSP-21065L is configured by writing to
its receive control register (SRCTL)—see ADSP-2106x SHARC
User’s Manual. Because the serial port within the ADSP-21065L
will be seeing a discontinuous clock, an initial word reading has
to be done after the ADSP-21065L has been reset to ensure that
the serial port is properly synchronized to this clock during each
following data read operation.
AD7676
*
ADSP-21065L
*
SHARC
SER/
PAR
RDC/SDIN
RFS
DR
RCLK
FLAG OR TFS
SYNC
SDOUT
SCLK
CNVST
RD
EXT/
INT
CS
INVSYNC
DVDD
*
ADDITIONAL PINS OMITTED FOR CLARITY
INVSCLK
Figure 23. Interfacing to the ADSP-21065L Using
the Serial Master Mode
APPLICATION HINTS
Layout
The AD7676 has very good immunity to noise on the power
supplies as can be seen in Figure 21. However, care should still
be taken with regard to grounding layout.
The printed circuit board that houses the AD7676 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 AD7676, or, at least, as close as possible to the
AD7676. If the AD7676 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 AD7676.
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 AD7676 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 AD7676 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 AD7676 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 corre-
sponding ground pins. Additionally, low ESR 10
μ
F capacitors
should be located in the vicinity of the ADC to further reduce
low-frequency ripple.
The DVDD supply of the AD7676 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 recom-
mended if no separate supply available, to connect the DVDD
digital supply to the analog supply AVDD through an RC filter
as shown in Figure 5, and connect the system supply to the inter-
face 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 AD7676 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 impor-
tant. The decoupling capacitor should be close to the ADC and
connected with short and large traces to minimize parasitic
inductances.
Evaluating the AD7676 Performance
A recommended layout for the AD7676 is outlined in the evalu-
ation board for the AD7676. The evaluation board package
includes a fully assembled and tested evaluation board, docu-
mentation, and software for controlling the board from a PC
via the Eval-Control BRD2.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7676ASTRL | 制造商:Analog Devices 功能描述:ADC Single SAR 500ksps 16-bit Parallel/Serial 48-Pin LQFP T/R |
| AD7676ASTZ | 功能描述:IC ADC 16BIT 500KSPS DIFF 48LQFP 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 |
| AD7676ASTZKL1 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| AD7676ASTZRL | 功能描述:IC ADC 16BIT DIFF INP 48LQFP 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:- 位數:14 采樣率（每秒）:83k 數據接口:串行，并聯 轉換器數目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應商設備封裝:28-PDIP 包裝:管件 輸入數目和類型:1 個單端，雙極 |
| AD7677 | 制造商:AD 制造商全稱:Analog Devices 功能描述:18-Bit, 2.5 LSB INL, 570 kSPS SAR ADC |
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