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參數資料
| 型號： | AD7898 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 5 V, 12-Bit, Serial 220 kSPS ADC in an 8-Lead Package |
| 中文描述： | 5伏，12位，220 kSPS的串行ADC的8引腳封裝 |
| 文件頁數： | 6/16頁 |
| 文件大小： | 184K |
| 代理商： | AD7898 |
AD7898
–6–
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 12-bit converter, this is 74 dB.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the rms sum of
harmonics to the fundamental. For the AD7898, 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. Normally, the value of this specification is 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
are 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 AD7898 is tested using the CCIF standard where two input
frequencies are used. 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
1 LSB change between any two adjacent codes in the ADC.
Positive Full-Scale Error (AD7898-10)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (4
×
VREF – 3/2 LSB) after the
Bipolar Zero Error has been adjusted out.
Positive Full-Scale Error (AD7898-3)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (VREF – 3/2 LSB) after the Bipolar
Zero Error has been adjusted out.
Bipolar Zero Error (AD7898-10, AD7898-3)
This is the deviation of the midscale transition (all 0s to all 1s)
from the ideal AGND – 1/2 LSB.
Negative Full-Scale Error (AD7898-10)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (–4
×
VREF + 1/2 LSB) after Bipo-
lar Zero Error has been adjusted out.
Negative Full-Scale Error (AD7898-3)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (–VREF + 1/2 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/
2 LSB, 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 AD7898. 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 start-
ing another conversion to ensure that the part operates to
specification.
PSR (Power Supply Rejection)
Variations in power supply will affect the full-scale transition,
but not the converter’s linearity. Power Supply Rejection is the
maximum change in full-scale transition point due to change in
power-supply voltage from the nominal value.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7898AR10 | 制造商:AD 功能描述:New |
| AD7898AR-10 | 功能描述:IC ADC 12BIT SRL HS 5V 8-SOIC RoHS:否 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 |
| AD7898AR-10 | 制造商:Analog Devices 功能描述:A/D CONVERTER (A-D) IC ((NW)) |
| AD7898AR-10REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 220ksps 12-bit Serial 8-Pin SOIC N T/R 制造商:Rochester Electronics LLC 功能描述:5V 12-BIT SERIAL ADC IN 8-PIN PKG I.C. - Tape and Reel |
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