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參數資料
| 型號： | AD7621AST |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 16-Bit, 1 LSB INL, 3 MSPS PulSAR ADC |
| 中文描述： | 1-CH 16-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL/PARALLEL ACCESS, PQFP48 |
| 封裝： | MO-026-BBC, LQFP-48 |
| 文件頁數： | 17/26頁 |
| 文件大小： | 265K |
| 代理商： | AD7621AST |
REV. Pr D
PRELIMINARY TECHNICAL DATA
AD7621
–17–
TYPICAL CONNECTION DIAGRAM
Figure 5 shows a typical connection diagram for the
AD7621. Different circuitry shown on this diagram are
optional and are discussed below.
Analog Inputs
Figure 6 shows a simplified analog input section of the
AD7621.
To Be Supplied
Figure 6. AD7621 simplified Analog Input.
The diodes shown in Figure 6 provide ESD protection for
the inputs. Care must be taken to ensure that the analog
input signal never exceeds the absolute ratings on these
inputs. This will cause these diodes to become forward-
biased and start conducting current. These diodes can
handle a forward-biased current of 150 mA maximum.
This condition could eventually occur when the input
buffer's (U1) or (U2) supplies are different from AVDD.
In such case, an input buffer with a short-circuit current
limitation can be used to protect the part.
This analog input structure is a true differential structure.
By using these differential inputs, signals common to both
inputs are rejected as shown in Figure 7 which represents
the typical CMRR over frequency.
To Be Supplied
Figure 7. Analog Input CMRR vs. Frequency
During the acquisition phase, for AC signals, the AD7621
behaves like a one pole RC filter consisted of the equiva-
lent resistance R+ , R-
and C
S
. The resistors R+ and R-
are typically TBD
and are lumped component made up
of some serial resistor and the on resistance of the switches.
The capacitor C
S
is typically TBD pF and is mainly the
ADC sampling capacitor. This one pole filter with a typi-
cal -3dB cutoff frequency of 50 MHz reduces undesirable
aliasing effect and limits the noise coming from the in-
puts.
Because the input impedance of the AD7621 is very high,
the AD7621 can be driven directly by a low impedance
source without gain error. That allows to put, as shown in
Figure 5, an external one-pole RC filter between the out-
put of the amplifier output and the ADC analog inputs to
even further improve the noise filtering done by the
AD7621 analog input circuit. However, the source imped-
ance has to be kept low because it affects the ac
performances, especially the total harmonic distortion.
The maximum source impedance depends on the amount
of total harmonic distortion (THD) that can be tolerated.
The THD degrades as a function of the source impedance
and the maximum input frequency.
Driver Amplifier Choice
Although the AD7621 is easy to drive, the driver amplifier
needs to meet at least the following requirements:
The driver amplifier and the AD7621 analog input
circuit have to be able together to settle for a full-scale
step the capacitor array at a 16-bit level (0.0015%). In
the amplifier’s datasheet, the settling at 0.1% or 0.01%
is more commonly specified. It could significantly dif-
fer from the settling time at 16 bit level and, therefore,
it should be verified prior to the driver selection. The
tiny op-amp AD8021 which combines ultra low noise
and a high gain bandwidth meets this settling time
requirement.
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相關代理商/技術參數 |
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| AD7621ASTRL | 制造商:Analog Devices 功能描述:ADC Single SAR 3Msps 16-bit Parallel/Serial 48-Pin LQFP T/R |
| AD7621ASTZ | 功能描述:IC ADC 16BIT 2MSPS DIFF 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 |
| AD7621ASTZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:16-Bit, 2 LSB INL, 3 MSPS PulSAR?? ADC |
| AD7621ASTZRL | 功能描述:IC ADC 16BIT 2MSPS DIFF 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 |
| AD7621ASTZRL1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:16-Bit, 2 LSB INL, 3 MSPS PulSAR?? ADC |
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