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

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.

ENBL

VOUT

VCC

NC

NC

VINN

VINP

IOUT

RSET

GND

NC

AD8290

NC

NC

NC

16

1

4

3

2

12

9

10

11

14

15

13

6.8nF

C1

0.1µF

CF2

CF1

5

6

7

8

C2

68nF

0.1µF

3kΩ

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

Excitation Current (μA)

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

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