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參數(shù)資料
| 型號： | AD7671ACPZRL |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 6/24頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC 16BIT CMOS 1MSPS 48LFCSP |
| 標準包裝： | 2,500 |
| 系列： | PulSAR® |
| 位數(shù)： | 16 |
| 采樣率（每秒）： | 1M |
| 數(shù)據(jù)接口： | 串行，并聯(lián) |
| 轉(zhuǎn)換器數(shù)目： | 1 |
| 功率耗散（最大）： | 125mW |
| 電壓電源： | 模擬和數(shù)字 |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 48-VFQFN 裸露焊盤，CSP |
| 供應商設備封裝： | 48-LFCSP-VQ（7x7） |
| 包裝： | 帶卷 (TR) |
| 輸入數(shù)目和類型： | 4 個單端，單極；4 個單端，雙極 |
| 配用： | EVAL-AD7671CBZ-ND - BOARD EVALUATION FOR AD7671 |
AD7671
–14–
Analog Inputs
The AD7671 is specified to operate with six full-scale analog input
ranges. Connections required for each of the four analog inputs,
IND, INC, INB, and INA, and the resulting full-scale ranges
are shown in Table I. The typical input impedance for each
analog input range is also shown.
Figure 6 shows a simplified analog input section of the AD7671.
The four resistors connected to the four analog inputs form a
resistive scaler that scales down and shifts the analog input range
to a common input range of 0 V to 2.5 V at the input of the
switched capacitive ADC.
INC
INB
INA
4R
2R
R
IND
4R
AGND
AVDD
R1
CS
R =
Figure 6. Simplified Analog Input
By connecting the four inputs INA, INB, INC, and IND to the
input signal itself, the ground, or a 2.5 V reference, other analog
input ranges can be obtained.
The diodes shown in Figure 6 provide ESD protection for the
four analog inputs. The inputs INB, INC, and IND have a high
voltage protection (–11 V to +30 V) to allow a wide input voltage
range. Care must be taken to ensure that the analog input signal
never exceeds the absolute ratings on these inputs, including
INA (0 V to 5 V). This will cause these diodes to become forward-
biased and start conducting current. These diodes can handle
a forward-biased current of 120 mA maximum. For instance,
when using the 0 V to 2.5 V input range, these conditions could
eventually occur on the input INA when the input buffer’s (U1)
supplies are different from AVDD. In such cases, an input buffer
with a short-circuit current limitation can be used to protect the part.
This analog input structure allows the sampling of the differen-
tial signal between the output of the resistive scaler and INGND.
Unlike other converters, the INGND input is sampled at the
same time as the inputs. By using this differential input, small
signals common to both inputs are rejected as shown in Figure 7,
which represents the typical CMRR over frequency. For instance,
by using INGND to sense a remote signal ground, the difference of
ground potentials between the sensor and the local ADC ground
is eliminated. During the acquisition phase for ac signals, the
AD7671 behaves like a one-pole RC filter consisting of the
equivalent resistance of the resistive scaler R/2 in series with R1
and CS. The resistor R1 is typically 100
W and is a lumped
component made up of some serial resistors and the on resis-
tance of the switches.
The capacitor CS is typically 60 pF and is mainly the ADC
sampling capacitor. This one-pole filter with a typical –3 dB
cutoff frequency of 9.6 MHz reduces undesirable aliasing effects
and limits the noise coming from the inputs.
40
35
50
45
60
55
70
65
75
1
10
100
1000
10000
CMRR
–
dB
FREQUENCY – kHz
Figure 7. Analog Input CMRR vs. Frequency
Except when using the 0 V to 2.5 V analog input voltage range,
the AD7671 has to be driven by a very low impedance source to
avoid gain errors. That can be done by using a driver amplifier
whose choice is eased by the primarily resistive analog input
circuitry of the AD7671.
When using the 0 V to 2.5 V analog input voltage range, the input
impedance of the AD7671 is very high so the AD7671 can be
driven directly by a low impedance source without gain error.
That allows, as shown in Figure 5, putting an external one-pole
RC filter between the output of the amplifier output and the
ADC analog inputs to even further improve the noise filtering
done by the AD7671 analog input circuit. However, the source
impedance has to be kept low because it affects the ac perfor-
mances, especially the total harmonic distortion (THD). The
maximum source impedance depends on the amount of total THD
that can be tolerated. The THD degradation is a function of the
source impedance and the maximum input frequency as shown
in Figure 8.
FREQUENCY – kHz
–110
0
100
THD
–
dB
–100
–90
–80
–70
1000
R = 100
R = 50
R = 11
Figure 8. THD vs. Analog Input Frequency and Input
Resistance (0 V to 2.5 V Only)
REV. C
375
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7671AST | 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 16-bit Parallel/Serial 48-Pin LQFP 制造商:Analog Devices 功能描述:IC 16-BIT ADC |
| AD7671ASTRL | 制造商:Analog Devices 功能描述:ADC Single SAR 1Msps 16-bit Parallel/Serial 48-Pin LQFP T/R 制造商:Rochester Electronics LLC 功能描述:16-BIT, 1MSPS CMOS ADC - Tape and Reel |
| AD7671ASTZ | 功能描述:IC ADC 16BIT CMOS 1MSPS 48-LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:PulSAR® 標準包裝:1 系列:microPOWER™ 位數(shù):8 采樣率（每秒）:1M 數(shù)據(jù)接口:串行，SPI? 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:- 電壓電源:模擬和數(shù)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(shù)目和類型:8 個單端，單極 產(chǎn)品目錄頁面:892 (CN2011-ZH PDF) 其它名稱:296-25851-6 |
| AD7671ASTZKL1 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| AD7671ASTZRL | 功能描述:IC ADC 16BIT CMOS 1MSPS 48LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:PulSAR® 標準包裝:1 系列:- 位數(shù):14 采樣率（每秒）:83k 數(shù)據(jù)接口:串行，并聯(lián) 轉(zhuǎn)換器數(shù)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(shù)目和類型:1 個單端，雙極 |
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