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參數資料
| 型號： | AD7705EB |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Precision Zero-Drift Operational Amplifier with Internal Capacitors; Package: SO; No of Pins: 8; Temperature Range: 0°C to +70°C |
| 中文描述： | 3伏/ 5伏1毫瓦2-/3-Channel 16位Σ-Δ模數轉換器（264.12十一） |
| 文件頁數： | 23/32頁 |
| 文件大小： | 264K |
| 代理商： | AD7705EB |
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AD7705/AD7706
–23–
REV. A
The printed circuit board that houses the AD7705 should be
designed so that the analog and digital sections are separated
and confined to certain areas of the board. This facilitates the
use of ground planes which can be separated easily. A minimum
etch technique is generally best for ground planes as it gives the
best shielding. Digital and analog ground planes should only be
joined in one place to avoid ground loops. If the AD7705/AD7706
is in a system where multiple devices require AGND-to-DGND
connections, the connection should be made at one point only,
a star ground point which should be established as close as
possible to the AD7705 GND.
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 AD7705/AD7706 to avoid noise coupling. The
power supply lines to the AD7705/AD7706 should use as large
a trace as possible to provide low impedance paths and reduce
the effects of glitches on the power supply line. Fast switching
signals like clocks should be shielded with digital ground to
avoid radiating noise to other sections of the board and clock
signals should never be run near the analog inputs. Avoid cross-
over of digital and analog signals. Traces on opposite sides of
the board should run at right angles to each other. This will
reduce the effects of feedthrough through the board. A micro-
strip technique is by far the best, but is not always possible with
a double-sided board. In this technique, the component side of
the board is dedicated to ground planes while signals are placed
on the solder side.
Good decoupling is important when using high resolution
ADCs. All analog supplies should be decoupled with 10
μ
F
tantalum in parallel with 0.1
μ
F ceramic capacitors to GND. To
achieve the best from these decoupling components, they have
to be placed as close as possible to the device, ideally right up
against the device. All logic chips should be decoupled with
0.1
μ
F disc ceramic capacitors to DGND.
Evaluating the AD7705/AD7706 Performance
The recommended layout for the AD7705 and AD7706 is out-
lined in their associated evaluation. These evaluation board
packages include a fully assembled and tested evaluation board,
documentation, software for controlling the board over the
printer port of a PC and software for analyzing their perfor-
mance on the PC.
Noise levels in the signals applied to the AD7705/AD7706 may
also affect performance of the part. The AD7705/AD7706 soft-
ware evaluation package allows the user to evaluate the true
performance of the part, independent of the analog input signal.
The scheme involves using a test mode on the part where the
inputs to the AD7705 are internally shorted together to provide
a zero differential voltage for the analog modulator. External to
the device, the AIN1(–) input on the AD7705 should be con-
nected to a voltage that is within the allowable common-mode
range of the part. Similarly, on the AD7706 the COMMON
input should be connected to a voltage within its allowable
common-mode range for evaluation purposes. This scheme should
be used after a calibration has been performed on the part.
DIGITAL INTERFACE
As previously outlined, the AD7705/AD7706’s programmable
functions are controlled using a set of on-chip registers. Data is
written to these registers via the part’s serial interface and read
access to the on-chip registers is also provided by this interface.
All communications to the part must start with a write operation
to the Communications Register. After power-on or RESET,
the device expects a write to its Communications Register. The
data written to this register determines whether the next opera-
tion to the part is a read or a write operation and also deter-
mines to which register this read or write operation occurs.
Therefore, write access to any of the other registers on the part
starts with a write operation to the Communications Register
followed by a write to the selected register. A read operation
from any other register on the part (including the output data
register) starts with a write operation to the Communications
Register followed by a read operation from the selected register.
The AD7705/AD7706’s serial interface consists of five signals,
CS
, SCLK, DIN, DOUT and
DRDY
. The DIN line is used for
transferring data into the on-chip registers while the DOUT line
is used for accessing data from the on-chip registers. SCLK is
the serial clock input for the device and all data transfers (either
on DIN or DOUT) take place with respect to this SCLK signal.
The
DRDY
line is used as a status signal to indicate when data
is ready to be read from the AD7705/AD7706’s data register.
DRDY
goes low when a new data word is available in the out-
put register. It is reset high when a read operation from the data
register is complete. It also goes high prior to the updating of
the output register to indicate when
not
to read from the device
to ensure that a data read is not attempted while the register is
being updated.
CS
is used to select the device. It can be used to
decode the AD7705/AD7706 in systems where a number of
parts are connected to the serial bus.
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相關代理商/技術參數 |
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| AD7706 | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V/5 V, 1 mW 2-/3-Channel 16-Bit, Sigma-Delta ADCs |
| AD7706BN | 功能描述:IC ADC 16BIT 3CH 16-DIP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數:12 采樣率（每秒）:3M 數據接口:- 轉換器數目:- 功率耗散（最大）:- 電壓電源:- 工作溫度:- 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 供應商設備封裝:SOT-23-6 包裝:帶卷 (TR) 輸入數目和類型:- |
| AD7706BNZ | 功能描述:IC ADC 16BIT 3CHAN 16DIP 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 |
| AD7706BNZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V/5 V, 1 mW, 2-/3-Channel, 16-Bit, Sigma-Delta ADCs |
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