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參數(shù)資料
| 型號(hào)： | ADC0820 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 8-Bit High Speed μP Compatible A/D Converter with Track/Hold Function(8位高速μP兼容A/D轉(zhuǎn)換器帶跟蹤/保持功能) |
| 中文描述： | CMOS、高速、8位A/D轉(zhuǎn)換器，帶有采樣/保持功能 |
| 文件頁數(shù)： | 15/22頁 |
| 文件大?。?/td> | 472K |
| 代理商： | ADC0820 |
2.0 Analog Considerations
(Continued)
2.3 INPUT FILTERING
It should be made clear that transients in the analog input
signal, caused by charging current flowing into V
, will not
degrade the A/D’s performance in most cases. In effect the
ADC0820 does not “l(fā)ook” at the input when these transients
occur. The comparators’ outputs are not latched while WR is
low, so at least 600 ns will be provided to charge the ADC’s
input capacitance. It is therefore not necessary to filter out
these transients by putting an external cap on the V
IN
termi-
nal.
2.4 INHERENT SAMPLE-HOLD
Another benefit of the ADC0820’s input mechanism is its
ability to measure a variety of high speed signals without the
help of an external sample-and-hold. In a conventional SAR
type converter, regardless of its speed, the input must re-
main at least
1
2
LSB stable throughout the conversion pro-
cess if full accuracy is to be maintained. Consequently, for
many high speed signals, this signal must be externally
sampled, and held stationary during the conversion.
Sampled-data comparators, by nature of their input switch-
ing, already accomplish this function to a large degree (Sec-
tion 1.2). Although the conversion time for the ADC0820 is
1.5 μs, the time through which V
must be
1
2
LSB stable is
much smaller. Since the MS flash ADC uses V
as its “com-
pare” input and the LS ADC uses V
as its “zero” input, the
ADC0820 only “samples” V
when WR is low (Sections 1.3
and 2.2). Even though the two flashes are not done simulta-
neously, the analog signal is measured at one instant. The
value of V
approximately 100 ns after the rising edge of
WR (100 ns due to internal logic prop delay) will be the mea-
sured value.
Input signals with slew rates typically below 100 mV/μs can
be converted without error. However, because of the input
time constants, and charge injection through the opened
comparator input switches, faster signals may cause errors.
Still, the ADC0820’s loss in accuracy for a given increase in
signal slope is far less than what would be witnessed in a
conventional successive approximation device.An SAR type
converter with a conversion time as fast as 1 μs would still
not be able to measure a 5V 1 kHz sine wave without the aid
of an external sample-and-hold. The ADC0820, with no such
help, can typically measure 5V, 7 kHz waveforms.
DS005501-24
FIGURE 14.
DS005501-25
FIGURE 15.
www.national.com
15
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADC0820 WAF | 制造商:Texas Instruments 功能描述: |
| ADC08200 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:8-Bit, 20 Msps to 200 Msps, Low Power A/D Converter with Internal Sample-and-Hold |
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| ADC08200CIMT | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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 |
| ADC08200CIMT/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 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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