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參數(shù)資料
| 型號： | ADS774JU |
| 英文描述： | Microprocessor-Compatible Sampling CMOS ANALOG-to-DIGITAL CONVERTER |
| 中文描述： | 微處理器兼容采樣CMOS模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 12/13頁 |
| 文件大?。?/td> | 413K |
| 代理商： | ADS774JU |
ADS774
12
connected either to Pin 9 (Analog Common) for unipolar
operation, or to Pin 8 (2.5V Ref Out), or the external
reference, for bipolar operation. Full-scale and offset adjust-
ments are described below.
The input impedance of the ADS774 is typically 50k
in the
20V ranges and 12k
in the 10V ranges. This is signifi-
cantly higher than that of traditional ADC774 architectures,
reducing the load on the input source in most applications.
INPUT STRUCTURE
Figure 12 shows the resistor divider input structure of the
ADS774. Since the input is driving a capacitor in the CDAC
during acquisition, the input is looking into a high imped-
ance node as compared with traditional ADC774 architec-
tures, where the resistor divider network looks into a com-
parator input node at virtual ground.
To understand how this circuit works, it is necessary to
know that the input range on the internal sampling capacitor
is from 0V to +3.33V, and the analog input to the ADS774
must be converted to this range. Unipolar 20V range can be
used as an example of how the divider network functions. In
20V operation, the analog input goes into pin 14. Pin 13 is
left unconnected and pin 12 is connected to pin 9, analog
common. From Figure 12, it is clear that the input to the
capacitor array will be the analog input voltage on pin 14
divided by the resistor network (42k
+ 42k
|| 10.5k
). A
20V input at pin 14 is divided to 3.33V at the capacitor
array, while a 0V input at pin 14 gives 0V at the capacitor
array.
The main effect of the 10k
internal resistor on pin 12 is to
provide the same offset adjust response as that of traditional
ADC774 architectures without changing the external trimpot
values.
SINGLE SUPPLY OPERATION
The ADS774 is designed to operate from a single +5V
supply, and handle all of the unipolar and bipolar input
ranges, in either the Control Mode or the Emulation Mode as
described above. Pin 7 is not connected internally. This is
FIGURE 10. Unipolar Configuration.
100
100
Analog
Common
100k
100k
+V
CC
–V
CC
R
1
Unipolar
Offset
Adjust
Full-Scale
Adjust
Ref In
Ref Out
Bipolar Offset
ADS774
10
8
12
13
14
9
10V
Range
Analog
Input
20V
Range
R
2
2.5V
R
3
The +5V supply should be bypassed with a 10
μ
F tantalum
capacitor located close to the converter to promote noise-
free operations, as shown in Figure 2. Noise on the power
supply lines can degrade the converter’s performance. Noise
and spikes from a switching power supply are especially
troublesome.
RANGE CONNECTIONS
The ADS774 offers four standard input ranges: 0V to +10V,
0V to +20V,
±
5V, or
±
10V. Figures 10 and 11 show the
necessary connections for each of these ranges, along with
the optional gain and offset trim circuits. If a 10V input
range is required, the analog input signal should be con-
nected to pin 13 of the converter. A signal requiring a 20V
range is connected to pin 14. In either case the other pin of
the two is left unconnected. Pin 12 (Bipolar Offset) is
100
10V
Range
Analog
Input
Analog
Common
Full-Scale Adjust
Ref In
Ref Out
Bipolar Offset
ADS774
10
8
12
13
14
9
20V
Range
Bipolar
Offset
Adjust
R
1
100
R
2
2.5V
FIGURE 11. Bipolar Configuration.
FIGURE 12. ADS774 Input Structure.
Capacitor
Array*
42k
21k
10.5k
10k
21k
Pin 12
Pin 13
Pin 14
20V Range
10V Range
Bipolar
Offset
*10pF when sampling
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS774JU/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Mcrprcsr-Compatible 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 |
| ADS774JU/1KE4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Mcrprcsr-Compatible 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 |
| ADS774JUE4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Mcrprcsr-Compatible 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 |
| ADS774JUG4 | 制造商:Texas Instruments 功能描述: |
| ADS774KE | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Mcrprcsr-Compatible 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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