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| 型号： | AD7679ACPZRL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 10/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC 18BIT SAR W/BUFF 48LFCSP |
| 标准包装： | 2,500 |
| 系列： | PulSAR® |
| 位数： | 18 |
| 采样率（每秒）： | 570k |
| 数据接口： | 串行，并联 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 103mW |
| 电压电源： | 模拟和数字 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-VFQFN 裸露焊盘，CSP |
| 供应商设备封装： | 48-LFCSP-VQ（7x7） |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 1 个差分，双极 |
| 配用： | EVAL-AD7679CBZ-ND - BOARD EVALUATION FOR AD7679 |
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AD7679
Rev. A | Page 18 of 28
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).
eN is the equivalent input noise voltage of each op amp in
nV/√Hz.
For instance, for a driver with an equivalent input noise of
2 nV/√Hz (e.g., AD8021) configured as a buffer, thus with
a noise gain of +1, the SNR degrades by only 0.34 dB with
the filter in Figure 25, and by 1.8 dB without it.
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.
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.
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 VREF, this configuration will produce a
differential ±VREF with midscale at VREF/2.
If the application can tolerate more noise, the AD8138,
differential driver can be used.
U2
8.25k
Ω
2.5V
AD8021
590
Ω
AD7679
IN+
IN– REF
U1
ANALOG INPUT
(UNIPOLAR
0V TO 4.096V)
10pF
AD8021
590
Ω
10pF
10
μF
100nF
1.82k
Ω
2.7nF
30
Ω
2.7nF
30
Ω
REFBUFIN
03085-0-031
Figure 29. Single-Ended-to-Differential Driver Circuit
(Internal Reference Buffer Used)
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.
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 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.
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.
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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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD7679AST | 制造商:Analog Devices 功能描述:ADC Single SAR 570ksps 18-bit Parallel/Serial 48-Pin LQFP 制造商:Analog Devices 功能描述:18BIT SAR ADC SMD 7679 LQFP48 |
| 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 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:PulSAR® 标准包装:1 系列:microPOWER™ 位数:8 采样率（每秒）:1M 数据接口:串行，SPI? 转换器数目:1 功率耗散（最大）:- 电压电源:模拟和数字 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘 供应商设备封装:24-VQFN 裸露焊盘（4x4） 包装:Digi-Reel® 输入数目和类型:8 个单端，单极 产品目录页面:892 (CN2011-ZH PDF) 其它名称: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 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:PulSAR® 标准包装:1 系列:- 位数:14 采样率（每秒）:83k 数据接口:串行，并联 转换器数目:1 功率耗散（最大）:95mW 电压电源:双 ± 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:28-DIP（0.600"，15.24mm） 供应商设备封装:28-PDIP 包装:管件 输入数目和类型:1 个单端，双极 |
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