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參數資料
| 型號： | AD7894AR-3 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | VARISTOR 320V RMS 14MM RADIAL |
| 中文描述： | 1-CH 14-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數： | 5/12頁 |
| 文件大小： | 131K |
| 代理商： | AD7894AR-3 |
AD7894
–5–
REV. 0
TERMINOLOGY
Signal to (Noise + Distortion) Ratio
This is the measured ratio of signal to (noise + distortion) at the
output of the A/D converter. The signal is the rms amplitude of
the fundamental. Noise is the rms sum of all nonfundamental
signals up to half the sampling frequency (f
S
/2), excluding dc.
The ratio is dependent upon the number of quantization levels
in the digitization process; the more levels, the smaller the quan-
tization noise. The theoretical signal to (noise + distortion) ratio
for an ideal N-bit converter with a sine wave input is given by:
Signal to
(
Noise
+
Distortion
) = (6.02
N
+ 1.76)
dB
Thus for a 14-bit converter, this is 86.04 dB.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the rms sum of
harmonics to the fundamental. For the AD7894, it is defined as:
THD dB
V
V
V
V
V
V
(
)
log
=
+
+
+
+
20
2
2
3
2
4
2
5
2
6
2
1
where
V
1
is the rms amplitude of the fundamental and
V
2
,
V
3
,
V
4
,
V
5
and
V
6
are the rms amplitudes of the second through the
sixth harmonics.
Peak Harmonic or Spurious Noise
Peak harmonic or spurious noise is defined as the ratio of the
rms value of the next largest component in the ADC output
spectrum (up to f
S
/2 and excluding dc) to the rms value of the
fundamental. The value of this specification is normally deter-
mined by the largest harmonic in the spectrum, but for parts
where the harmonics are buried in the noise floor, it will be a
noise peak.
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
is equal to zero. For example, the second order
terms include (fa + fb) and (fa – fb), while the third order terms
include (2 fa + fb), (2 fa – fb), (fa + 2 fb) and (fa – 2 fb).
The AD7894 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 second
and third order terms are specified separately. The calculation
of the intermodulation distortion is as per the THD specification
where it is the ratio of the rms sum of the individual distortion
products to the rms amplitude of the fundamental expressed
in dBs.
Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum
deviation from a straight line passing through the endpoints of
the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal 1LSB
change between any two adjacent codes in the ADC.
Positive Gain Error (AD7894-10)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (4
×
VREF – 1 LSB) after the
Bipolar Zero Error has been adjusted out.
Positive Gain Error (AD7894-3)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (VREF – 1 LSB) after the Bipolar
Zero Error has been adjusted out.
Positive Gain Error (AD7894-2)
This is the deviation of the last code transition (11 . . . 110 to
11 . . . 111) from the ideal (VREF – 1 LSB) after the Unipolar
Offset Error has been adjusted out.
Bipolar Zero Error (AD7894-10, AD7894-3)
This is the deviation of the midscale transition (all 0s to all 1s)
from the ideal 0 V (GND).
Unipolar Offset Error (AD7894-2)
This is the deviation of the first code transition (00 . . . 000 to
00 . . . 001) from the ideal 1 LSB.
Negative Gain Error (AD7894-10)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (–4
×
VREF + 1 LSB) after Bipolar
Zero Error has been adjusted out.
Negative Gain Error (AD7894-3)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (– VREF + 1 LSB) after Bipolar
Zero Error has been adjusted out.
Track/Hold Acquisition Time
Track/Hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within
±
1/2LSB, after the end of conversion (the point at which the
track/hold returns to track mode). It also applies to situations
where there is a step input change on the input voltage applied
to the V
IN
input of the AD7894. This means that the user must
wait for the duration of the track/hold acquisition time after the
end of conversion or after a step input change to V
IN
before
starting another conversion, to ensure that the part operates to
specification.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7894AR-3REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 200ksps 14-bit Serial 8-Pin SOIC N T/R |
| AD7894AR-3REEL7 | 制造商:Analog Devices 功能描述:ADC Single SAR 200ksps 14-bit Serial 8-Pin SOIC N T/R 制造商:Rochester Electronics LLC 功能描述:SERIAL 14-BIT ADC I.C. - Tape and Reel |
| AD7894ARZ-10 | 功能描述:IC ADC 14BIT SRL T/H LP 8SOIC RoHS:是 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 其它有關文件:TSA1204 View All Specifications 標準包裝:1 系列:- 位數:12 采樣率（每秒）:20M 數據接口:并聯 轉換器數目:2 功率耗散（最大）:155mW 電壓電源:模擬和數字 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-TQFP 供應商設備封裝:48-TQFP（7x7） 包裝:Digi-Reel® 輸入數目和類型:4 個單端，單極；2 個差分，單極 產品目錄頁面:1156 (CN2011-ZH PDF) 其它名稱:497-5435-6 |
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| AD7894ARZ-10REEL7 | 功能描述:IC ADC 14BIT SRL T/H LP 8SOIC RoHS:是 類別:集成電路 (IC) >> 數據采集 - 模數轉換器 系列:- 標準包裝:1,000 系列:- 位數:12 采樣率（每秒）:300k 數據接口:并聯 轉換器數目: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） 供應商設備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數目和類型:1 個單端，單極；1 個單端，雙極 |
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