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| 型號(hào)： | AD7865AS-3 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | Four-Channel, Simultaneous Sampling, Fast, 14-Bit ADC |
| 中文描述： | 4-CH 14-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PQFP44 |
| 封裝： | PLASTIC, QFP-44 |
| 文件頁(yè)數(shù)： | 16/19頁(yè) |
| 文件大小： | 195K |
| 代理商： | AD7865AS-3 |
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AD7865
–16–
REV. A
ADC CODE
7000
0
C
6000
5000
4000
3000
2000
1000
Figure 14. Histogram of 8192 Conversions of a DC Input
The output spectrum from the ADC is evaluated by applying a
sine wave signal of very low distortion to the analog input. A
Fast Fourier Transform (FFT) plot is generated from which the
SNR data can be obtained. Figure 15 shows a typical 4096-
point FFT plot of the AD7865 with an input signal of 100 kHz
and a sampling frequency of 350 kHz. The SNR obtained from
this graph is 80.5 dB. It should be noted that the harmonics are
taken into account when calculating the SNR.
FREQUENCY – Hz
–140
d
0
35000
70000
105000
140000
175000
fs = 100kHz
f
SNR = 80.5dB
–120
–100
–80
–60
–40
–20
0
Figure 15. 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
obtain 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 16 shows a typical plot of
effective number of bits versus frequency for an AD7865-2.
INPUT FREQUENCY – kHz
0
E
0
100
1000
10000
–55
8
C
+25
8
C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
+125
8
C
Figure 16. Effective Numbers of Bits vs. Frequency
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa
±
nfb where
m, n = 0, 1, 2, 3 . . ., etc. Intermodulation terms are those for
which neither m nor n are equal to zero. For example, the sec-
ond order terms include (fa + fb) and (fa – fb) while the third
order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).
The AD7865 is tested using two input frequencies. In this case
the second and third order terms are of different significance.
The second order terms are usually distanced in frequency from
the original sine waves while the third order terms are usually at
a frequency close to the input frequencies. As a result, the sec-
ond and third order terms are specified separately. The calcula-
tion of the intermodulation distortion is as per the THD specifi-
cation where it is the ratio of the rms sum of the individual
distortion products to the rms amplitude of the fundamental
expressed in dBs. In this case, the input consists of two, equal
amplitude, low distortion sine waves. Figure 17 shows a typical
IMD plot for the AD7865.
FREQUENCY – Hz
0
–140
d
0
25000
50000
100000
125000
175000
75000
150000
–120
–100
–80
–60
–40
–20
f
a
= 49.113kHz
f
b
= 50.183kHz
fs = 350kHz
Figure 17. IMD Plot
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7865AS-3REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 350ksps 14-bit Parallel 44-Pin MQFP T/R |
| AD7865ASZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:Four-Channel, Simultaneous Sampling, Fast, 14-Bit ADC |
| AD7865ASZ-1 | 功能描述:IC ADC 14BIT DUAL 4CH 44-MQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)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(yīng)商設(shè)備封裝:24-VQFN 裸露焊盤（4x4） 包裝:Digi-Reel® 輸入數(shù)目和類型:8 個(gè)單端，單極 產(chǎn)品目錄頁(yè)面:892 (CN2011-ZH PDF) 其它名稱:296-25851-6 |
| AD7865ASZ-1REEL | 功能描述:IC ADC 14BIT 4CHAN 5V 44-MQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1,000 系列:- 位數(shù):12 采樣率（每秒）:300k 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:75mW 電壓電源:單電源 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:24-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數(shù)目和類型:1 個(gè)單端，單極；1 個(gè)單端，雙極 |
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