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參數(shù)資料
| 型號： | LM4120AI-4.1 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 串行ADC |
| 英文描述： | Self-Calibrating 12-Bit Plus Sign Serial I/O A/D Converters with MUX and Sample/Hold |
| 中文描述： | 自校準12位帶符號串行I /辦公自動化/ D轉(zhuǎn)換器MUX和采樣/保持 |
| 文件頁數(shù)： | 33/41頁 |
| 文件大?。?/td> | 1152K |
| 代理商： | LM4120AI-4.1 |
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Application Hints
(Continued)
3.0 REFERENCE VOLTAGE
The difference in the voltages applied to the V
REF+
and
V
REF
defines the analog input span (the difference between
the voltage applied between two multiplexer inputs or the
voltage applied to one of the multiplexer inputs and analog
ground), over which 4095 positive and 4096 negative codes
exist. The voltage sources driving V
REF+
or V
REF
must have
very low output impedance and noise. The circuit in
Figure
16
is an example of a very stable reference appropriate for
use with the device.
The ADC 12030/2/4/8 can be used in either ratiometric or
absolute reference applications. In ratiometric systems, the
analog input voltage is proportional to the voltage used for
the ADC’s reference voltage. When this voltage is the sys-
tem power supply, the V
REF+
pin is connected to V
A+
and
V
REF
is connected to ground. This technique relaxes the
system reference stability requirements because the analog
input voltage and the ADC reference voltage move together.
This maintains the same output code for given input condi-
tions. For absolute accuracy, where the analog input voltage
varies between very specific voltage limits, a time and tem-
perature stable voltage source can be connected to the
reference inputs. Typically, the reference voltage’s magni-
tude will require an initial adjustment to null reference volt-
age induced full-scale errors.
Below are recommended references along with some key
specifications.
Output
Voltage
Tolerance
±
0.5%
±
0.1%
±
0.2%
±
0.2%
±
0.1
±
0.05%
±
2.2
±
0.4
±
0.1%
Adjustable
Temperature
Coefficient
Part Number
LM4041CI-Adj
LM4040AI-4.1
LM4120AI-4.1
LM4121AI-4.1
LM4050AI-4.1
LM4030AI-4.1
LM4031AI
LM4031AC
LM4140AC-4.1
Circuit of
Figure 16
±
100ppm/C
±
100ppm/C
±
50ppm/C
±
50ppm/C
±
50ppm/C
±
10ppm/C
±
26ppm/C
±
46ppm/C
±
3.0ppm/C
±
2ppm/C
The reference voltage inputs are not fully differential. The
ADC12030/2/4/8 will not generate correct conversions or
comparisons if V
REF+
is taken below V
REF
. Correct conver-
sions result when V
REF+
and V
REF
differ by 1V and remain,
at all times, between ground and V
A+
. The V
REF
common
mode range, (V
REF+
+ V
REF
)/2 is restricted to (0.1 x V
A+
) to
(0.6 x V
A+
). Therefore, with V
A+
= 5V the center of the
reference ladder should not go below 0.5V or above 3.0V.
Figure 17
is a graphic representation of the voltage restric-
tions on V
REF+
and V
REF
.
01135450
FIGURE 15. Fully Differential Biasing
01135442
*
Tantalum
FIGURE 16. Low Drift Extremely
Stable Reference Circuit
A
www.national.com
33
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM4120AIM50 | 制造商:Texas Instruments 功能描述: |
| LM4120AIM5-1.8 | 功能描述:基準電壓& 基準電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓撲結(jié)構:Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4120AIM5-1.8 | 制造商:Texas Instruments 功能描述:IC SM MICROPOWER REFERENCE 1.8V |
| LM4120AIM5-1.8/NOPB | 功能描述:基準電壓& 基準電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓撲結(jié)構:Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
| LM4120AIM5-2.0 | 功能描述:基準電壓& 基準電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓撲結(jié)構:Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
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