Transfer function
2
STLM20
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
(first order linear equation)
V O = ( – 11.69mV ) ⁄ ° C × T + 1.8663 V
Over the specified operating temperature range, the best accuracy can be obtained by using
the parabolic transfer function:
Equation 2
(second order parabolic equation)
VO = (–3.88 × 10 −6 × T 2 ) + (–1.15 × 10 –2 × T ) + 1.8639
and solving for T:
T = –1481 .96 + 2.1962 × 10 6 +
(1.8639 − VO )
3.88 × 10 – 6
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
6/19
Tmin (°C)
Tmax (°C)
VO =
Maximum deviation of linear
equation from parabolic equation
(°C)
–55
130
–11.79 mV/°C * T + 1.8528 V
±1.41
–40
110
–11.77 mV/°C * T + 1.8577 V
±0.93
–30
100
–11.77 mV/°C * T + 1.8605 V
±0.70
–40
85
–11.67 mV/°C * T + 1.8583 V
±0.65
–10
65
–11.71 mV/°C * T + 1.8641 V
±0.23
35
45
–11.81 mV/°C * T + 1.8701 V
±0.004
20
30
–11.69 mV/°C * T + 1.8663 V
±0.004
Linear equation
Doc ID 12495 Rev 13