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AD7714ARS-5 参数 Datasheet PDF下载

AD7714ARS-5图片预览
型号: AD7714ARS-5
PDF下载: 下载PDF文件 查看货源
内容描述: 3 V / 5 V , CMOS , 500微安信号调理ADC [3 V/5 V, CMOS, 500 uA Signal Conditioning ADC]
分类和应用: 转换器光电二极管
文件页数/大小: 40 页 / 308 K
品牌: ADI [ ADI ]
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AD7714  
RTD Measurement  
If the buffer is required, the common-mode voltage should be  
set accordingly by inserting a small resistance between the bot-  
tom end of the RTD and AGND of the AD7714. In the appli-  
cation shown an external 400 µA current source provides the  
excitation current for the PT100 and it also generates the refer-  
ence voltage for the AD7714 via the 6.25 kresistor. Variations  
in the excitation current do not affect the circuit as both the  
input voltage and the reference voltage vary ratiometrically with  
the excitation current. However, the 6.25 kresistor must have  
a low temperature coefficient to avoid errors in the reference  
voltage over temperature.  
Figure 14 shows another temperature measurement application  
for the AD7714. In this case, the transducer is an RTD (Resis-  
tive Temperature Device), a PT100. The arrangement is a 4-  
lead RTD configuration. There are voltage drops across the lead  
resistances RL1 and RL4 but these simply shift the common-  
mode voltage. There is no voltage drop across lead resistances  
RL2 and RL3 as the input current to the AD7714 is very low. The  
lead resistances present a small source impedance so it would  
not generally be necessary to turn on the buffer on the AD7714.  
+5V  
AV  
DV  
DD  
DD  
400A  
REF IN (+)  
AV  
AD7714  
DD  
6.25k⍀  
1A  
REF IN (–)  
AIN1  
CHARGE BALANCING A/D  
STANDBY  
CONVERTER  
R
L1  
AUTO-ZEROED  
DIGITAL  
SYNC  
MODULATOR  
⌺⌬  
R
PGA  
FILTER  
L2  
BUFFER  
RTD  
AIN2  
A = 1–128  
MCLK IN  
CLOCK  
R
L3  
GENERATION  
SERIAL INTERFACE  
REGISTER BANK  
1A  
MCLK OUT  
AGND  
R
L4  
RESET  
AGND  
DGND  
DRDY  
POL  
BUFFER  
DOUT  
DIN  
CS  
SCLK  
Figure 14. RTD Measurement Using the AD7714  
–36–  
REV. C  
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