STLM20

Transfer function

7/17

2

Transfer function

The STLM20’s transfer function can be described in different ways, with varying levels of

precision. A simple linear transfer function, with good accuracy near 25°C is expressed as:

Equation 1

Over the specified operating temperature range, the best accuracy can be obtained by using

the parabolic transfer function:

Equation 2

and solving for T:

Equation 3

The best fit linear transfer function for many popular temperature ranges was calculated in

Table 2, where the error introduced by the linear transfer function increases with wider

temperature ranges.

Table 2.

First order equations optimized for different temperature ranges

Temperature range

Linear equation

Maximum deviation of linear

equation from parabolic equation

(°C)

–55

130

–11.79mV/°C * T + 1.8528V

±1.41

–40

110

–11.77mV/°C * T + 1.8577V

±0.93

–30

100

–11.77mV/°C * T + 1.8605V

±0.70

–40

85

–11.67mV/°C * T + 1.8583V

±0.65

–10

65

–11.71mV/°C * T + 1.8641V

±0.23

35

45

–11.81mV/°C * T + 1.8701V

±0.004

20

30

–11.69mV/°C * T + 1.8663V

±0.004

V

O

11 69mV

∴

–

∴

+

×

⁄

=

V

O

388

∴

10

6

–

T

2

×

×

–

()

115

∴

–

10

2

–

T

×

×

∴

++

=

T

1481 96

∴

–

21962

∴

10

6

1 8639

∴

V

O

–

()

388

∴

10

6

–

×

-----------------------------------

+

×

+

=