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參數(shù)資料
| 型號： | ADS7807PBG4 |
| 英文描述： | Low-Power, 16-Bit, Sampling CMOS ANALOG-to-DIGITAL CONVERTER |
| 中文描述： | 低功耗，16位，采樣CMOS模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大?。?/td> | 534K |
| 代理商： | ADS7807PBG4 |
ADS7807
SBAS022C
17
www.ti.com
amount of charge injection due to the sampling FET switch
on the ADS7807 is approximately 5% to 10% of the amount
on similar A/D converters with the charge redistribution
Digital-to-Analog Converter (DAC) CDAC architecture. There
is also a resistive front end which attenuates any charge
which is released. The end result is a minimal requirement for
the drive capability on the signal conditioning preceding the
A/D converter. Any op amp sufficient for the signal in an
application will be sufficient to drive the ADS7807.
The resistive front end of the ADS7807 also provides a speci-
fied
±
25V over-voltage protection. In most cases, this elimi-
nates the need for external over-voltage protection circuitry.
INTERMEDIATE LATCHES
The ADS7807 does have tri-state outputs for the parallel
port, but intermediate latches should be used if the bus will
be active during conversions. If the bus is not active during
conversion, the tri-state outputs can be used to isolate the
A/D converter from other peripherals on the same bus.
Intermediate latches are beneficial on any monolithic A/D
converter. The ADS7807 has an internal LSB size of 38
μ
V.
Transients from fast switching signals on the parallel port,
even when the A/D converter is tri-stated, can be coupled
through the substrate to the analog circuitry causing degra-
dation of converter performance.
APPLICATIONS INFORMATION
TRANSITION NOISE
Apply a DC input to the ADS7807 and initiate 1000 conver-
sions. The digital output of the converter will vary in output
codes due to the internal noise of the ADS7807. This is true
for all 16-bit SAR converters. The transition noise specifica-
tion found in the electrical characteristics section is a statis-
tical figure which represents the one sigma limit or rms value
of these output codes.
Using a histogram to plot the output codes, the distribution
should appear bell-shaped with the peak of the bell curve
representing the nominal output code for the input voltage
value. The
±
1
σ
,
±
2
σ
, and
±
3
σ
distributions will represent
68.3%, 95.5%, and 99.7% of all codes. Multiplying TN by 6
will yield the
±
3
σ
distribution or 99.7% of all codes. Statisti-
cally, up to 3 codes could fall outside the 5 code distribution
when executing 1000 conversions. The ADS7807 has a TN
of 0.8LSBs which yields 5 output codes for a
±
3
σ
distribution.
Figures 12 and 13 show 1000 and 10000 conversion histo-
gram results.
AVERAGING
The noise of the converter can be compensated by averag-
ing the digital codes. By averaging conversion results, tran-
sition noise will be reduced by a factor of 1/
√
Hz
where n is
FIGURE 13. Histogram of 10000 Conversions with Input Grounded.
FIGURE 12. Histogram of 1000 Conversions with Input Grounded.
the number of averages. For example, averaging four con-
version results will reduce the TN by 1/2 to 0.4LSBs. Aver-
aging should only be used for input signals with frequencies
near DC.
For AC signals, a digital filter can be used to low-pass filter
and decimate the output codes. This works in a similar
manner to averaging: for every decimation by 2, the signal-
to-noise ratio will improve 3dB.
52
FFFE
H
173
FFFF
H
581
0000
H
176
0001
H
18
0002
H
0
0
0003
H
FFFD
H
438
FFFE
H
1681
FFFF
H
5671
0000
H
176
0001
H
2010
182
0002
H
0
18
0003
H
FFFD
H
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS7807PG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Low-Power 16-Bit Sampling CMOS RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7807U | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Low-Power 16-Bit Sampling CMOS RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7807U/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Low-Power 16-Bit Sampling CMOS RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7807U/1KE4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Low-Power 16-Bit Sampling CMOS RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS7807U/1KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Low-Power 16-Bit Sampling CMOS RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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