AN2648

STLM20 temperature-to-output transfer function

5/15

Given that the expected voltage range is less than 0.5 V, it should be possible to amplify the

STLM20 output signal so that is uses more of the available voltage range. A 10x

amplification should be possible without exceeding the available 5 V range. Furthermore, a

positive slope is more intuitive to the user, so inverting it would be helpful, too. Hence, a

gain of –10 should be used. Multiplying equation 1 by –10, we get the curve as shown at the

bottom in Figure 5.

Figure 5.

Application transfer function after gain, inversion and offset

The result has positive slope and spans from –17.5 to –12.8, an interval of about 4.7 V,

much closer to the available 5 V range.

-18.5

-16.5

-14.5

-12.5

-10.5

-8.5

-6.5

-4.5

-2.5

-0.5

1.5

3.5

5.5

-50

-30

-10

10

30

50

70

90

Temperature, T (˚C)

+17.5

< 5V

ai13989

x –10