- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄373915 > AD7725 (Analog Devices, Inc.) 16-Bit 900 kSPS ADC with a Programmable Postprocessor PDF資料下載
參數(shù)資料
| 型號： | AD7725 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 16-Bit 900 kSPS ADC with a Programmable Postprocessor |
| 中文描述： | 16位900 ksps模數(shù)轉(zhuǎn)換器的可編程后處理器 |
| 文件頁數(shù)： | 15/28頁 |
| 文件大小： | 442K |
| 代理商： | AD7725 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁當前第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁
REV. A
AD7725
–15–
CIRCUIT DESCRIPTION
The AD7725 employs a -
conversion technique to convert
the analog input into an equivalent digital word. The modulator
samples the input waveform and outputs an equivalent digital
word at the input clock frequency, f
CLKIN
.
Due to the high oversampling rate, which spreads the quantiza-
tion noise from 0 to f
CLKIN
/2, the noise energy contained in the
band of interest is reduced (Figure 9a). To further reduce the
quantization noise, a high order modulator is employed to shape
the noise spectrum so that most of the noise energy is shifted
out of the band of interest (Figure 9b).
The digital filtering that follows the modulator removes the
large out-of-band quantization noise (Figure 9c) while also
reducing the data rate from f
CLKIN
at the input of the filter to
f
CLKIN
/16 or less at the output of the filter, depending on the
filter type used.
Digital filtering has certain advantages over analog filtering.
Because digital filtering occurs after the A/D conversion, it can
remove noise injected during the conversion process. Analog
filtering cannot do this. The digital filter also has a linear
phase response.
a.
b.
c.
QUANTIZATION NOISE
NOISE SHAPING
DIGITAL FILTER CUTOFF FREQUENCY
f
CLKIN
/2
f
CLKIN
/2
f
CLKIN
/2
BAND OF INTEREST
BAND OF INTEREST
BAND OF INTEREST
Figure 9. - ADC
The AD7725 employs three fixed finite impulse response (FIR)
filters in series. Each individual filter’s output data rate is half
that of its input data rate. The fourth stage is programmable;
the user can select a range of different filter responses at this
stage. Both the filter response and the decimation are user pro-
grammable. See the Filtering section for more details.
APPLYING THE AD7725
Analog Input Range
The AD7725 has differential inputs to provide common-mode
noise rejection. In unipolar mode, the analog input is single-
ended and its range is 0 V to (8/5 V
REF2
). In bipolar mode,
the analog input is single-ended or differential, and its input
range is
±
(4/5 V
REF2
). The output code is twos complement
in both modes with 1 LSB = 61
μ
V.
The ideal input/output transfer characteristics for the two
modes are shown in Figure 10. In both modes, the absolute
voltage on each input must remain within the supply range
AGND to AV
DD
. Bipolar mode allows either single-ended or
differential input signals while unipolar mode allows single-
ended signals.
DIFFERENTIAL INPUT VOLTAGE, V
IN
(+) – V
IN
(–)
011...111
–4/5 V
REF2
(0V)
0V
(4/5 V
REF2
)
O
4/5 V
REF2
– 1LSB
(8/5 V
REF2
– 1LSB)
BIPOLAR
UNIPOLAR
011...110
000...010
000...001
000...000
111...111
111...110
100...001
100...000
Figure 10. Bipolar/(Unipolar) Mode Transfer Function
The AD7725 will accept full-scale inband signals; however,
large scale out-of-band signals can overload the modulator inputs.
A minimal single-pole RC antialias filter set to f
CLKIN
/24 will allow
full-scale input signals over the entire frequency spectrum.
Analog Input
The analog input of the AD7725 uses a switched capacitor
technique to sample the input signal. For the purpose of driving
the AD7725, an equivalent circuit of the analog inputs is shown
in Figure 11. For each half-clock cycle, two highly linear sam-
pling capacitors are switched to both inputs, converting the
input signal into an equivalent sampled charge. A signal source
driving the analog inputs must be able to source this charge,
while also settling to the required accuracy by the end of each
half-clock phase.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD7725BS | 16-Bit 900 kSPS ADC with a Programmable Postprocessor |
| AD7729 | Dual Sigma-Delta ADC with Auxiliary DAC |
| AD7729AR | Dual Sigma-Delta ADC with Auxiliary DAC |
| AD7729ARU | Dual Sigma-Delta ADC with Auxiliary DAC |
| AD7730LBR | Bridge Transducer ADC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7725BS | 制造商:Analog Devices 功能描述:ADC Single Delta-Sigma 900ksps 16-bit Parallel/Serial 44-Pin MQFP 制造商:Rochester Electronics LLC 功能描述:16-BIT PROGRAMMABLE SIGMA-DELTA ADC I.C. - Bulk 制造商:Analog Devices 功能描述:IC 16BIT ADC SMD 7725 MQFP44 |
| AD7725BSC-REEL | 制造商:Analog Devices 功能描述: |
| AD7725BS-REEL | 制造商:Analog Devices 功能描述:ADC Single Delta-Sigma 900ksps 16-bit Parallel/Serial 44-Pin MQFP T/R 制造商:Rochester Electronics LLC 功能描述:16-BIT PROGRAMMABLE SIGMA-DELTA ADC I.C. - Tape and Reel |
| AD7725BSZ | 功能描述:IC ADC 16BIT PROG 44MQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數(shù):12 采樣率（每秒）:3M 數(shù)據(jù)接口:- 轉(zhuǎn)換器數(shù)目:- 功率耗散（最大）:- 電壓電源:- 工作溫度:- 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 供應(yīng)商設(shè)備封裝:SOT-23-6 包裝:帶卷 (TR) 輸入數(shù)目和類型:- |
| AD7727BCPZRL | 制造商:Analog Devices 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。