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參數(shù)資料
| 型號(hào)： | AD7874ARZ |
| 廠商： | Analog Devices Inc |
| 文件頁(yè)數(shù)： | 15/16頁(yè) |
| 文件大?。?/td> | 0K |
| 描述： | IC DAS 12BIT 4CH 5V 28-SOIC |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 類(lèi)型： | 數(shù)據(jù)采集系統(tǒng)（DAS） |
| 分辨率（位）： | 12 b |
| 采樣率（每秒）： | 116k |
| 數(shù)據(jù)接口： | 并聯(lián) |
| 電壓電源： | 雙 ± |
| 電源電壓： | ±5V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類(lèi)型： | 表面貼裝 |
| 封裝/外殼： | 28-SOIC（0.295"，7.50mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 28-SOIC W |
| 包裝： | 管件 |
| 產(chǎn)品目錄頁(yè)面： | 776 (CN2011-ZH PDF) |
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AD7874
REV. C
–8–
The first read operation to the AD7874 after conversion always
accesses data from Data Register 1 (i.e., the conversion result
from the VIN1 input). INT is reset high on the falling edge of
RD
during this first read operation. The second read always ac-
cesses data from Data Register 2 and so on. The address pointer
is reset to point to Data Register 1 on the rising edge of
CONVST
. A read operation to the AD7874 should not be at-
tempted during conversion. The timing diagram for the
AD7874 conversion sequence is shown in Figure 7.
CH1
DATA
CH2
DATA
CH3
DATA
CH4
DATA
INT
CS
RD
CONVST
HIGH-IMPEDANCE
TRACK/HOLDS GO
INTO HOLD
HIGH-
Z
HIGH-Z
t
1
t
CONV
t
ACQUISITION
t
5
t
2
t
8
t
4
t
3
t
7
t
6
HIGH-
Z
HIGH-
Z
TIMES
t
2, t3, t4, t6, t7, AND t8 ARE THE SAME FOR ALL FOUR READ OPERATIONS.
Figure 7. AD7874 Timing Diagram
AD7874 DYNAMIC SPECIFICATIONS
The AD7874 is specified and 100% tested for dynamic perfor-
mance specifications as well as traditional dc specifications such
as Integral and Differential Nonlinearity. These ac specifications
are required for the signal processing applications such as
phased array sonar, adaptive filters and spectrum analysis.
These applications require information on the ADC’s effect on
the spectral content of the input signal. Hence, the parameters
for which the AD7874 is specified include SNR, harmonic dis-
tortion, intermodulation distortion and peak harmonics. These
terms are discussed in more detail in the following sections.
Signal-to-Noise Ratio (SNR)
SNR is the measured signal to noise ratio at the output of the
ADC. The signal is the rms magnitude of the fundamental.
Noise is the rms sum of all the nonfundamental signals up to
half the sampling frequency (fs/2) excluding dc. SNR is depen-
dent upon the number of quantization levels used in the digiti-
zation process; the more levels, the smaller the quantization
noise. The theoretical signal to noise ratio for a sine wave input
is given by
SNR = (6.02N + 1.76) dB
(1)
where N is the number of bits.
Thus for an ideal 12-bit converter, SNR = 74 dB.
The output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the VIN input which is
sampled at a 29 kHz sampling rate. A Fast Fourier Transform
(FFT) plot is generated from which the SNR data can be ob-
tained. Figure 8 shows a typical 2048 point FFT plot of the
AD7874BN with an input signal of 10 kHz and a sampling
frequency of 29 kHz. The SNR obtained from this graph is
73.2 dB. It should be noted that the harmonics are taken into
account when calculating the SNR.
Figure 8. AD7874 FFT Plot
Effective Number of Bits
The formula given in Equation 1 relates the SNR to the number
of bits. Rewriting the formula, as in Equation 2, it is possible to
get a measure of performance expressed in effective number of
bits (N).
N
= SNR 1.76
6.02
(2)
The effective number of bits for a device can be calculated di-
rectly from its measured SNR.
Figure 9 shows a typical plot of effective number of bits versus
frequency for an AD7874BN with a sampling frequency of
29 kHz. The effective number of bits typically falls between
11.75 and 11.87 corresponding to SNR figures of 72.5 dB and
73.2 dB.
z
Figure 9. Effective Numbers of Bits vs. Frequency
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7874ARZ-REEL | 功能描述:IC DAS 12BIT 4CH 5V 28-SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:40-TQFN-EP（6x6） 包裝:托盤(pán) |
| AD7874ARZ-REEL7 | 功能描述:IC DAS 12BIT 4CH 5V 28SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:- 產(chǎn)品培訓(xùn)模塊:Data Converter Basics 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:電機(jī)控制 分辨率（位）:12 b 采樣率（每秒）:1M 數(shù)據(jù)接口:串行，并聯(lián) 電壓電源:單電源 電源電壓:2.7 V ~ 3.6 V，4.5 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:100-TQFP 供應(yīng)商設(shè)備封裝:100-TQFP（14x14） 包裝:剪切帶 (CT) 其它名稱(chēng):296-18373-1 |
| AD7874BN | 功能描述:IC DAS 12BIT 4CH 5V 28-DIP RoHS:否 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:40-TQFN-EP（6x6） 包裝:托盤(pán) |
| AD7874BNZ | 功能描述:IC DAS 12BIT 4CH 5V 28-DIP RoHS:是 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:40-TQFN-EP（6x6） 包裝:托盤(pán) |
| AD7874BQ | 功能描述:IC DAS 12BIT 4CH 5V 28-CDIP RoHS:否 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:40-TQFN-EP（6x6） 包裝:托盤(pán) |
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