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