Datasheet

AD8290
Rev. B | Page 19 of 20
TEMPERATURE SENSOR APPLICATION
The AD8290 can be used with a temperature sensor. Figure 48
shows the AD8290 in conjunction with an RTD, in this
example, a 2-wire PT100. The specifications for the sensor are
shown in
Table 8 and the chosen conditions for the AD8290 are
listed in
Table 9.
Once again, care must be taken when picking the excitation
current and R
G
such that the minimum and maximum
specifications of the AD8290 are not exceeded. Sample
calculations are shown in
Table 10.
ADC/MICROCONTROLLER
In both of the previous applications, an ADC or a microcontroller
can be used to follow the AD8290 to convert the output analog
signal to digital. For example, if there are multiple sensors in the
system, the six channel ADuC814ARU microcontoller is an
excellent candidate to interface with multiple AD8290s.
06745-044
ENBL
VOUT
VCC
NC NC
VINN
VINP
IOUT
RSET
GND
NC
AD8290
NC NC NC
161
4
3
2
129
10
11
14
15
13
C
FILTER
6.8nF
C1
0.1µF
CF2CF1
56
7
8
C2
68nF
C
BRIDGE
0.1µF
R
SET
3kΩ
R
G
698Ω
RTD
3.3V
NC = NO CONNECT
Figure 48. PT100 Temperature Sensor Application Connections
Table 8. PT100 Specifications
RTD Minimum @ 0°C RTD Maximum @ 100°C
100 Ω 138.5 Ω
Table 9. Typical AD8290 Conditions for Temperature Sensor Circuit
AD8290 V
CC
(V) Excitation Current (μA) Resistor from RTD to GND, R
G
(Ω)
3.30 (2.6 to 5.5) 300 (300 to 1300) 698
Table 10. Temperature Sensor Circuit Calculations Compared to AD8290 Minimum/Maximum Specifications
Specification Calculation Unit Allowable Range of AD8290
Supply Current 1.8 mA
Current Setting Resistor (R
SET
) 3000 Ω 692 Ω to 3000 Ω
Minimum Equivalent Resistance to IOUT Pin 798 Ω
Maximum Equivalent Resistance to IOUT Pin 836.5 Ω
Minimum Voltage @ Current Output Pin (IOUT) 0.239 V >0.0 V
Maximum Voltage @ Current Output Pin (IOUT) 0.251 V <2.3 V
Input Voltage Minimum 0.209 V >0.2 V
Input Voltage Maximum 0.251 V <1.6 V
Output Voltage Minimum 2.365 V >0.075 V
Output Voltage Maximum 3.013 V <3.225 V