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參數(shù)資料
| 型號： | AD7869 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Complete 14-bit I/O System Containing a DAC and a ADC(完備的14位I/O系統(tǒng)（包含一個A/D轉(zhuǎn)換器和一個D/A轉(zhuǎn)換器）) |
| 中文描述： | 完整的14位I / O系統(tǒng)含的DAC和ADC的（完備的14位的I / O系統(tǒng)（包含一個的A / D轉(zhuǎn)換器和一個的D / A轉(zhuǎn)換器）） |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 308K |
| 代理商： | AD7869 |
AD7869
–9–
REV. A
Figure 9. ADC FFT Plot
Figure 10 shows a typical plot of effective number of bits versus
frequency for an AD7869AQ with a sampling frequency of
60 kHz. T he effective number of bits typically falls between 12.7
and 13.1, corresponding to SNR figures of 79 dB and 80.4 dB.
Figure 10. Effective Number of Bits vs. Frequency for the
ADC
DAC T esting
A simplified diagram of the method used to test the dynamic
performance specifications of the DAC is outlined in Figure 11.
Data is loaded to the DAC under control of the microcontroller
and associated logic. T he output of the DAC is applied to a 9th
order low pass filter whose cutoff frequency corresponds to the
Nyquist limit. T he output of the filter is, in turn, applied to a
16-bit accurate digitizer. T his digitizes the signal and the micro-
controller generates an FFT plot from which the dynamic per-
formance of the DAC can be evaluated.
AD7869
DAC
LOW-PASS
FILTER
16-BIT
DIGITIZER
MICRO-
CONTROLLER
Figure 11. DAC Dynamic Performance Test Circuit
AD7869 DY NAMIC SPE CIFICAT IONS
T he AD7869 is specified and 100% tested for dynamic perfor-
mance specifications as well as traditional dc specifications such
as Integral and Differential Nonlinearity. T hese ac specifications
are required for signal processing applications such as speech
recognition, spectrum analysis and high speed modems. T hese
applications require information on the converter’s effect on the
spectral content of the input signal. Hence, the parameters for
which the AD7869 is specified include SNR, harmonic distor-
tion and peak harmonics. T hese terms are discussed in more de-
tail in the following sections.
Signal-to-Noise Ratio (SNR)
SNR is the measured signal-to-noise ratio at the output of the
ADC or DAC. T he signal is the rms magnitude of the funda-
mental. Noise is the rms sum of all the nonfundamental signals
up to half the sampling frequency (f
SAMPLE
/2), excluding dc.
SNR is dependent upon the number of levels used in the quanti-
zation process; the more levels, the smaller the quantization
noise. T he theoretical signal-to-noise ratio for a sine wave input
is given by
SNR
= (6.02
N
+ 1.76)
dB
(1)
where
N
is the number of bits. T hus for an ideal 14-bit con-
verter,
SNR
= 86 dB.
E ffective Number of Bits
T he formula given in Equation (1) relates the SNR to the num-
ber of bits. Rewriting the formula, as in Equation (2), it is pos-
sible to obtain a measure of performance expressed in effective
number of bits (N).
N
=
SNR
±1.76
6.02
(2)
T he effective number of bits for a device can be calculated di-
rectly from its measured SNR.
Harmonic Distortion
Harmonic Distortion is the ratio of the rms sum of harmonics to
the fundamental. For the AD7869, total harmonic distortion
(T HD) is defined as:
THD
=
20log
V
2
2
+
V
32
+
V
42
+
V
52
+
V
62
V
1
where V1 is the rms amplitude of the fundamental and V2, V3,
V4, V5 and V6 are the rms amplitudes of the second through to
the sixth harmonic. T he T HD is also derived from the FFT plot
of the ADC or DAC output spectrum.
ADC T esting
T he output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the V
IN
input while
reading multiple conversion results. A Fast Fourier T ransform
(FFT ) plot is generated from which the SNR data can be ob-
tained. Figure 9 shows a typical 2048 point FFT plot of the
AD7869AQ ADC with an input signal of 10 kHz and a sam-
pling frequency of 60 kHz. T he SNR obtained from this graph
is 80 dB. It should be noted that the harmonics are taken into
account when calculating the SNR.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7869AQ | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete, 14-Bit Analog I/O System |
| AD7869JN | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete, 14-Bit Analog I/O System |
| AD7869JNZ | 功能描述:IC I/O PORT 14BIT ANLG 24DIP RoHS:是 類別:集成電路 (IC) >> 接口 - 專用 系列:- 特色產(chǎn)品:NXP - I2C Interface 標準包裝:1 系列:- 應用:2 通道 I²C 多路復用器 接口:I²C，SM 總線 電源電壓:2.3 V ~ 5.5 V 封裝/外殼:16-TSSOP（0.173"，4.40mm 寬） 供應商設(shè)備封裝:16-TSSOP 包裝:剪切帶 (CT) 安裝類型:表面貼裝 產(chǎn)品目錄頁面:825 (CN2011-ZH PDF) 其它名稱:568-1854-1 |
| AD7869JQ | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| AD7869JR | 制造商:Analog Devices 功能描述:Data Acquisition System Single ADC Single DAC 14-Bit 28-Pin SOIC W 制造商:Analog Devices 功能描述:DATA ACQ SYS SGL ADC SGL DAC 14BIT 28SOIC W - Rail/Tube |
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