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參數資料
| 型號： | AD7679AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 18-Bit, 2.5 LSB INL, 570 kSPS SAR ADC |
| 中文描述： | 1-CH 18-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL/PARALLEL ACCESS, PQFP48 |
| 封裝： | LOW PROFILE, MS-026BBC, LQFP-48 |
| 文件頁數： | 18/28頁 |
| 文件大小： | 1186K |
| 代理商： | AD7679AST |
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AD7679
Rev. 0 | Page 18 of 28
U2
8.25k
2.5V
AD8021
10pF
590
AD7679
IN+
IN–REF
U1
ANALOG INPUT
(UNIPOLAR
0V TO 4.096V)
10pF
AD8021
590
10
μ
F
100nF
1.82k
2.7nF
30
2.7nF
30
REFBUFIN
03085-0-031
The SNR degradation due to the amplifier is
=
π
+
2
)
(
625
25
log
20
N
3dB
–
LOSS
Ne
f
SNR
where:
f
–
3dB
is the –3 dB input bandwidth in MHz of the AD7679
(26 MHz) or the cutoff frequency of the input filter, if used.
N
is the noise factor of the amplifiers (1 if in buffer
configuration).
e
N
is the equivalent input noise voltage of each op amp in
nV/
√
Hz.
Figure 29. Single-Ended-to-Differential Driver Circuit
(Internal Reference Buffer Used)
For instance, for a driver with an equivalent input noise of
2 nV/
√
Hz (e.g., AD8021) configured as a buffer, thus with a
the filter in Figure 25, and by 1.8 dB without it. Voltage Reference
The AD7679 allows the use of an external voltage reference
either with or without the internal reference buffer.
Using the internal reference buffer is recommended when
sharing a common reference voltage between multiple ADCs is
desired.
The driver needs to have a THD performance suitable to
that of the AD7679.
The
AD8021
meets these requirements and is usually
appropriate for almost all applications. The AD8021 needs a
10 pF external compensation capacitor, which should have good
linearity as an NPO ceramic or mica type.
However, the advantages of using the external reference voltage
directly are
The SNR and dynamic range improvement (about 1.7 dB)
resulting from the use of a reference voltage very close to
the supply (5 V) instead of a typical 4.096 V reference when
the internal buffer is used.
The
AD8022
could be used if a dual version is needed and gain
of 1 is present. The
AD829
is an alternative in applications
where high frequency (above 100 kHz) performance is not
required. In gain of 1 applications, it requires an 82 pF
compensation capacitor. The
AD8610
is another option when
low bias current is needed in low frequency applications.
The power saving when the internal reference buffer is
powered down (PDBUF high).
To use the internal reference buffer, PDBUF should be LOW. A
2.5 V reference voltage applied on the REFBUFIN input will
result in a 4.096 V reference on the REF pin.
Single-to-Differential Driver
For applications using unipolar analog signals, a single-ended-
to-differential driver will allow for a differential input into the
part. The schematic is shown in Figure 29. When provided an
input signal of 0 to V
REF
, this configuration will produce a
differential ±V
REF
with midscale at V
REF
/2.
In both cases, the voltage reference input REF has a dynamic
input impedance and therefore requires an efficient decoupling
between REF and REFGND inputs. The decoupling consists of a
low ESR 47 μF tantalum capacitor connected to the REF and
REFGND inputs with minimum parasitic inductance.
If the application can tolerate more noise, the AD8138,
differential driver can be used.
Care should also be taken with the reference temperature
coefficient of the voltage reference, which directly affects the
full-scale accuracy if this parameter matters. For instance, a
±4 ppm/°C temperature coefficient of the reference changes the
full scale by ±1 LSB/°C.
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PDF描述 |
|---|---|
| AD7679ASTRL | 18-Bit, 2.5 LSB INL, 570 kSPS SAR ADC |
| AD7675 | 16-Bit, 100 kSPS, Differential ADC |
| AD7675AST | 16-Bit, 100 kSPS, Differential ADC |
| AD7675ASTRL | 16-Bit, 100 kSPS, Differential ADC |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7679ASTRL | 制造商:Analog Devices 功能描述:ADC Single SAR 570ksps 18-bit Parallel/Serial 48-Pin LQFP T/R 制造商:Analog Devices 功能描述:ADC SGL SAR 570KSPS 18BIT PARALLEL/SERL 48LQFP - Tape and Reel |
| AD7679ASTZ | 功能描述:IC ADC 18BIT 570KSPS 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 |
| AD7679ASTZ | 制造商:Analog Devices 功能描述:IC 18-BIT ADC |
| AD7679ASTZRL | 功能描述:IC ADC 18BIT SAR W/BUFF 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 |
| AD7679CB1 | 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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