REV. C

TMP35/TMP36/TMP37

–9–

The circuit in Figure 6b illustrates how a pair of TMP3x sensors

can be used with an OP193 configured as a difference amplifier

to read the difference in temperature between two locations. In

these applications, it is always possible that one temperature

sensor would be reading a temperature below that of the other

sensor. To accommodate this condition, the output of the OP193

is offset to a voltage at one-half the supply via R5 and R6. Thus,

the output voltage of the circuit is measured relative to this point,

OP193

0.1 F

2

3

4

1

7

@ 10mV/ C FOR TMP35/36

@ 20mV/ C FOR TMP35/36

FOR R1 = R2 = R3 = R;

3

R1

300k

R2

300k

R3

300k

TMP3x

TMP3x

TMP3x

R4

7.5k

R1

3

R4 = R6

R6

7.5k

R5

100k

R5 =

Figure 6a. Configuring Multiple Sensors for Average

Temperature Measurements

ELEMENT

R2

R4

R5

R6

TMP36

R1

50k

ADM660

TMP36

OP193

R2

50k

R3

R4

+3V

C1

10 F

R5

0.1 F

10 F

–3V

10 F/0.1 F

GND

NC

10 F

NC

R6

1

2

3

4

5

6

7

2

3

4

6

8

8

–40 F

+257 F

258.6k

10k

47.7k

10k

Figure 5c. TMP36 Fahrenheit Thermometer Version 2

as shown in the figure. Using the TMP36, the output voltage of

the circuit is scaled by 10 mV/

°C. To minimize error in the differ-

ence between the two measured temperatures, a common, readily

available thin-film resistor network is used for R1–R4.

TMP36

@ T1

0.1 F

0.1 F

2

3

4

6

7

OP193

1 F

R3*

R4*

R2*

R1*

TMP36

@ T2

R5

100k

R6

100k

2

*R1–R4, CADDOCK T914–100k–100, OR EQUIVALENT

0.1 F

R7

100k

R8

25k

R9

25k

0

125 C

CENTERED AT

CENTERED AT

Figure 6b. Configuring Multiple Sensors for Differential

Temperature Measurements