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參數資料
| 型號： | AD7715* |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 3 V/5 V. 450 uA 16-Bit. Sigma-Delta ADC |
| 中文描述： | 3 V / 5號五，450微安16位。 Σ-Δ模數轉換器 |
| 文件頁數： | 28/31頁 |
| 文件大小： | 474K |
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REV. C
AD7715
–28–
Temperature Measurement
Another application area for the AD7715 is in temperature
measurement. Figure 13 outlines a connection from a thermo-
couple to the AD7715. In this application, the AD7715 is oper-
ated in its buffered mode to allow large decoupling capacitors
on the front end to eliminate any noise pickup which there may
have been in the thermocouple leads. When the AD7715 is
operated in buffered mode, it has a reduced common-mode
range. In order to place the differential voltage from the thermo-
couple on a suitable common-mode voltage, the AIN(–) input of
the AD7715 is biased up at the reference voltage, +2.5V.
Figure 14 shows another temperature measurement application
for the AD7715. 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 R
L1
and R
L4
, but these simply shift the common-
mode voltage. There is no voltage drop across lead resistances
R
L2
and R
L3
as the input current to the AD7715 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 AD7715.
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 AD7715. In the appli-
cation shown an external 400
μ
A current source provides the
excitation current for the PT100 and it also generates the refer-
ence voltage for the AD7715 via the 6.25 k
resistor. 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 6.25k
resistor must have
a low temperature coefficient to avoid errors in the reference
voltage over temperature.
AUTO-ZEROED
MODULATOR
CHARGE BALANCING A/D
CONVERTER
DIGITAL
FILTER
AV
DD
SERIAL INTERFACE
REGISTER BANK
MCLK IN
MCLK OUT
REF IN (+)
REF IN (–)
AGND
DGND
DOUT
DIN
CS
SCLK
DRDY
RESET
DV
DD
AD7715
+5V
AIN (+)
AIN (–)
A = 1–128
PGA
BUFFER
CLOCK
GENERATION
GND
C
C
V
OUT
REF192
THERMOCOUPLE
JUNCTION
+5V
+V
IN
R
R
Figure 13. Thermocouple Measurement Using the AD7715
400
m
A
R
L4
R
L3
R
L2
R
L1
RTD
6.25k
V
AUTO-ZEROED
MODULATOR
CHARGE BALANCING A/D
CONVERTER
DIGITAL
FILTER
AV
DD
SERIAL INTERFACE
REGISTER BANK
MCLK IN
MCLK OUT
REF IN (+)
REF IN (–)
AGND
DGND
DOUT
DIN
CS
SCLK
DRDY
RESET
DV
DD
AD7715
+5V
AIN(+)
AIN(–)
A = 1–128
PGA
BUFFER
CLOCK
GENERATION
Figure 14. RTD Measurement Using the AD7715
相關PDF資料 |
PDF描述 |
|---|---|
| AD7715ACHIPS-3 | 3 V/5 V, 450 uA 16-Bit, Sigma-Delta ADC |
| AD7715ACHIPS-5 | 3 V/5 V, 450 uA 16-Bit, Sigma-Delta ADC |
| AD7719BRU | Low Voltage, Low Power, Factory-Calibrated 16-/24-Bit Dual ADC |
| AD7719 | Low Voltage, Low Power, Factory-Calibrated 16-/24-Bit Dual ADC |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD7715_10 | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V/5 V, 450 ??A 16-Bit, Sigma-Delta ADC |
| AD7715-5EB | 制造商:Analog Devices 功能描述: |
| AD7715ACHIPS-3 | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V/5 V, 450 uA 16-Bit, Sigma-Delta ADC |
| AD7715ACHIPS-5 | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 V/5 V, 450 uA 16-Bit, Sigma-Delta ADC |
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