TMP35/TMP36/TMP37

Rev. F | Page 11 of 20

The same circuit principles can be applied to the TMP36, but

because of the inherent offset of the TMP36, the circuit uses only

two resistors, as shown in Figure 26. In this circuit, the output

voltage transfer characteristic is 1 mV/°F but is referenced to

the common ground of the circuit; however, there is a 58 mV

(58°F) offset in the output voltage. For example, the output

voltage of the circuit reads 18 mV if the TMP36 is placed in a

−40°F ambient environment and 315 mV at +257°F.

At the expense of additional circuitry, the offset produced by

the circuit in Figure 26 can be avoided by using the circuit in

Figure 27. In this circuit, the output of the TMP36 is conditioned

by a single-supply, micropower op amp, the OP193. Although

the entire circuit operates from a single 3 V supply, the output

voltage of the circuit reads the temperature directly, with a

transfer characteristic of 1 mV/°F, without offset. This is accom-

plished through an ADM660, which is a supply voltage inverter.

The 3 V supply is inverted and applied to the V− terminal of the

OP193. Thus, for a temperature range between −40°F and +257°F,

the output of the circuit reads −40 mV to +257 mV. A general

expression for the transfer equation of the circuit is given by

TMP36

GND

0.1µF

R1

45.3kΩ

R2

10kΩ

()

⎟

⎠

⎞

⎜

⎝

⎛

⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

=

2

1

S

OUT

V

R3

R4

TMP36

R3

R4

R6

R5

R6

V

Figure 26. TMP36 Fahrenheit Thermometer Version 1

ELEMENT

R3

R4

R5

R6

VALUE

R1

50kΩ

ADM660

TMP36

OP193

R2

50kΩ

R3

R4

+3V

C1

10µF

R5

0.1µF

10µF

–3V

10µF/0.1µF

GND

NC

10µF

NC

R6

1

2

3

4

5

6

7

2

3

4

6

7

8

258.6kΩ

10kΩ

47.7kΩ

10kΩ

+

+

+

+

–

+

Figure 27. TMP36 Fahrenheit Thermometer Version 2