- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄378278 > ADC0820 (National Semiconductor Corporation) 8-Bit High Speed μP Compatible A/D Converter with Track/Hold Function(8位高速μP兼容A/D轉換器帶跟蹤/保持功能) PDF資料下載
參數(shù)資料
| 型號： | 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轉換器帶跟蹤/保持功能) |
| 中文描述： | CMOS、高速、8位A/D轉換器，帶有采樣/保持功能 |
| 文件頁數(shù)： | 14/22頁 |
| 文件大?。?/td> | 472K |
| 代理商： | ADC0820 |
2.0 Analog Considerations
2.1 REFERENCE AND INPUT
The two V
inputs of theADC0820 are fully differential and
define the zero to full-scale input range of the A to D con-
verter. This allows the designer to easily vary the span of the
analog input since this range will be equivalent to the voltage
difference
between
V
IN
(+)
V
(V
=V
(+)V
()) to less than 5V, the sensitivity
of the converter can be increased (i.e., if V
=2V then 1
LSB=7.8 mV). The input/reference arrangement also facili-
tates ratiometric operation and in many cases the chip power
supply can be used for transducer power as well as the V
REF
source.
This reference flexibility lets the input span not only be varied
but also offset from zero. The voltage at V
() sets the in-
put level which produces a digital output of all zeroes.
Though V
is not itself differential, the reference design af-
fords nearly differential-input capability for most measure-
ment applications. Figure 13 shows some of the configura-
tions that are possible.
and
V
().
By
reducing
2.2 INPUT CURRENT
Due to the unique conversion techniques employed by the
ADC0820, the analog input behaves somewhat differently
than in conventional devices. The A/D’s sampled-data com-
parators take varying amounts of input current depending on
which cycle the conversion is in.
The equivalent input circuit of the ADC0820 is shown in Fig-
ure 14 When a conversion starts (WR low, WR-RD mode),
all input switches close, connecting V
to thirty-one 1 pF ca-
pacitors. Although the two 4-bit flash circuits are not both in
their compare cycle at the same time, V
still sees all input
capacitors at once. This is because the MS flash converter is
connected to the input during its compare interval and the LS
flash is connected to the input during its zeroing phase (Sec-
tion 1.3). In other words, the LS ADC uses V
IN
as its
zero-phase input.
The input capacitors must charge to the input voltage
through the on resistance of the analog switches (about 5 k
to 10 k
). In addition, about 12 pF of input stray capacitance
must also be charged. For large source resistances, the ana-
log input can be modeled as an RC network as shown in Fig-
ure 15 As R
increases, it will take longer for the input ca-
pacitance to charge.
In RD mode, the input switches are closed for approximately
800 ns at the start of the conversion. In WR-RD mode, the
time that the switches are closed to allow this charging is the
time that WR is low. Since other factors force this time to be
at least 600 ns, input time constants of 100 ns can be ac-
commodated without special consideration. Typical total in-
put capacitance values of 45 pF allow R
to be 1.5 k
with-
out lengthening WR to give V
IN
more time to settle.
External Reference 2.5V Full-Scale
DS005501-21
Power Supply as Reference
DS005501-22
Input Not Referred to GND
DS005501-23
FIGURE 13. Analog Input Options
www.national.com
14
相關PDF資料 |
PDF描述 |
|---|---|
| ADC08234CIMF | IC,QUAD,UART,FIFO |
| ADC08238 | 16 A SPDT MINIATURE POWER RELAY |
| ADC08238BIN | 8-Bit 2 ms Serial I/O A/D Converters with MUX, Reference, and Track/Hold |
| ADC08238BIWM | 8-Bit 2 ms Serial I/O A/D Converters with MUX, Reference, and Track/Hold |
| ADC08231CIWM | 8-Bit 2 ms Serial I/O A/D Converters with MUX, Reference, and Track/Hold |
相關代理商/技術參數(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 |
| ADC08200_08 | 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 |
| ADC08200CIMT | 功能描述:模數(shù)轉換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADC08200CIMT/NOPB | 功能描述:模數(shù)轉換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結構:Sigma-Delta 轉換速率: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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-32 |
發(fā)布緊急采購，3分鐘左右您將得到回復。