Datasheet

Data Sheet AD7171
Rev. A | Page 13 of 16
APPLICATIONS INFORMATION
The AD7171 provides a low cost, high resolution analog-to-
digital function. Because the analog-to-digital function is
provided by a Σ-Δ architecture, the part is more immune to
noisy environments, making it ideal for use in sensor measure-
ment and industrial and process-control applications.
TEMPERATURE SYSTEM
Figure 13 shows the AD7171 used in a temperature measure-
ment system. The thermistor is connected in series with a
precision resistor, R
REF
, the precision resistor being used to
generate the reference voltage. The value of R
REF
is equal to the
maximum resistance produced by the thermistor. The complete
dynamic range of the ADC is then used, resulting in optimum
performance. See Table 7 for suitable external R-C
combinations.
16-BIT Σ-Δ
ADC
AD7171
GND
V
DD
INTERNAL
CLOCK
V
DD
R
REF
REFIN(+)
AIN(+)
AIN(–)
REFIN(–)
SCLK
DOUT/RDY
PDRST
08417-013
Figure 13. Temperature System Using the AD7171
SIGNAL CONDITIONING CIRCUIT
Figure 14 shows the AD7171 used in a signal conditioning
circuit for a single-ended analog input. In a low side shunt
current monitor, a low resistance shunt resistor converts the
current to voltage. The resulting voltage is amplified and
applied to the AD7171.
08417-018
AD7171
REFIN(+)
AIN(+)
AIN(–)
REFIN(–)
GND
V
DD
INTERNAL
CLOCK
SCLK
DOUT/RDY
AD5041
AD8628
1µF
ANALOG
INPUT
1kΩ
32kΩ
16-BIT
Σ-Δ ADC
Figure 14. Signal Conditioning Circuit