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| 型号： | AD7685CRMZRL7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 7/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC 16BIT PSEUDO-DIFF 10MSOP |
| 产品培训模块： | Power Line Monitoring Motor Control |
| 设计资源： | Parametric Measurement Unit and Supporting Components for PAD Appls Using AD5522 and AD7685 (CN0104) Integrated Device Power Supply for PAD with Output Voltage Range 0 V to 25 V (CN0130) |
| 标准包装： | 1,000 |
| 系列： | PulSAR® |
| 位数： | 16 |
| 采样率（每秒）： | 250k |
| 数据接口： | DSP，MICROWIRE?，QSPI?，串行，SPI? |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 15mW |
| 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 10-MSOP |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 1 个伪差分，单极 |
| 配用： | EVAL-AD7685CBZ-ND - BOARD EVAL FOR AD7685 |
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AD7685
Rev. C | Page 15 of 28
ANALOG INPUTS
Figure 28 shows an equivalent circuit of the input structure of
the AD7685.
The two diodes, D1 and D2, provide ESD protection for the
analog inputs IN+ and IN. Care must be taken to ensure that
the analog input signal never exceeds the supply rails by more
than 0.3 V because this will cause these diodes to begin to
forward-bias and start conducting current. These diodes can
handle a forward-biased current of 130 mA maximum. For
instance, these conditions could eventually occur when the
input buffer’s (U1) supplies are different from VDD. In such a
case, an input buffer with a short-circuit current limitation can
be used to protect the part.
CIN
RIN
D1
D2
CPIN
IN+
OR IN–
GND
VDD
02
96
8-
02
6
Figure 28. Equivalent Analog Input Circuit
This analog input structure allows the sampling of the
differential signal between IN+ and IN. By using this
differential input, small signals common to both inputs are
rejected, as shown in Figure 29, which represents the typical
CMRR over frequency. For instance, by using IN to sense a
remote signal ground, ground potential differences between
the sensor and the local ADC ground are eliminated.
02
96
8-
0
27
FREQUENCY (kHz)
10000
1
10
100
1000
CM
RR
(
d
B)
80
70
60
50
40
VDD = 5V
VDD = 2.5V
Figure 29. Analog Input CMRR vs. Frequency
During the acquisition phase, the impedance of the analog
inputs (IN+ or IN) can be modeled as a parallel combination
of capacitor CPIN and the network formed by the series connection
of RIN and CIN. CPIN is primarily the pin capacitance. RIN is
typically 3 kΩ and is a lumped component made up of some
serial resistors and the on resistance of the switches. CIN is
typically 30 pF and is mainly the ADC sampling capacitor.
During the conversion phase, where the switches are opened,
the input impedance is limited to CPIN. RIN and CIN make a
1-pole, low-pass filter that reduces undesirable aliasing effects
and limits the noise.
When the source impedance of the driving circuit is low, the
AD7685 can be driven directly. Large source impedances
significantly affect the ac performance, especially THD. The dc
performances are less sensitive to the input impedance. The
maximum source impedance depends on the amount of THD
that can be tolerated. The THD degrades as a function of the
source impedance and the maximum input frequency, as shown
in Figure 30.
02
96
8-
0
28
FREQUENCY (kHz)
100
0
255075
T
H
D
(
d
B)
–60
–70
–80
–90
–100
–110
–120
RS = 33
RS = 50
RS = 100
RS = 250
Figure 30. THD vs. Analog Input Frequency and Source Resistance
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD7685-C-U2 | 制造商:Analog Devices 功能描述:250 KSPS 16-BIT PULSAR? A/D CONVERTER IN ?SOIC - Bulk |
| AD7685-S-U2 | 制造商:Analog Devices 功能描述:250 KSPS 16-BIT PULSAR? A/D CONVERTER - Bulk |
| AD7685XRM-U3 | 制造商:Analog Devices 功能描述:A/D CONVERTER 250KSPS 16-BIT PULSAR - Bulk |
| AD7686 | 制造商:AD 制造商全称:Analog Devices 功能描述:16-Bit, +/-0.65 LSB INL, 500 kSPS PulSAR Differential ADC in MSOP/QFN |
| AD76861 | 制造商:AD 制造商全称:Analog Devices 功能描述:18-Bit, 2 MSPS PulSAR 15 mW ADC in LFCSP (QFN) |
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