TMP20 datasheet(7/18 Pages) TI1

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2.19262

10 +(1.8639

V )

3.88

-6

T= 1481.96+

TMP20

www.ti.com

SBOS466 – DECEMBER 2009

APPLICATION INFORMATION

Linear transfer functions can be calculated for limited

OVERVIEW

temperature ranges by calculating the slope and

offset for that limited range, where slope is calculated

The TMP20 is a precision analog output temperature

by:

sensor. The temperature range of operation is –55°C

to +130°C with supply voltages of 2.7V to 5.5V. The

m = –7.76 x 10–6 x T – 0.0115

TMP20 can operate from power-supply voltages as

low as 1.8V over a temperature range of +15°C to

with T equal to the temperature at the middle of the

+130°C.

temperature range of interest.

Power-supply bypassing is recommended; use a

The offset in the linear transfer function is found by:

100nF capacitor placed as closely as possible to the

b = [VOUT(TMAX) + VOUT(T) – m x (TMAX + T)]/2

supply pin.

where VOUT(TMAX) is the calculated output voltage at

TRANSFER FUNCTION

TMAX as determined from the parabolic transfer

function.

The analog output of the TMP20 over the –55°C to

+130°C

temperature

range

corresponds

the

VOUT(T) is then the calculated output voltage at T as

parabolic transfer function:

determined by using the parabolic transfer function.

VOUT = (–3.88 × 10

–6 × T2) + (–1.15 × 10–2 × T) +

Example 1

1.8639V

Determine the linear transfer function for –40°C to

Where the temperature T is in °C.

+110°C.

When solved for temperature, the equation is:

TMIN = –40°C; TMAX = +110°C; therefore, T = +35°C

m = –11.77mV/°C

VOUT (110°C) = 0.5520V

VOUT (35°C) = 1.4566V

These equations apply over the entire operating

range, –55°C to +130°C.

b = 1.8576V

A simplified linear transfer function for near +25°C

Therefore, the linear transfer function for –40°C to

measurement is:

+110°C is:

VOUT = –11.69mV/°C x T + 1.8663V.

VOUT = –11.77mV/°C x T + 1.8576V

space

Table 1 shows many common temperature ranges of

interest

and

the

corresponding

linear

transfer

space

functions for these ranges. Note that the error

(maximum deviation) of the linear equation from the

space

parabolic equation increases as the temperature

ranges widen.

Table 1. Common Temperature Ranges and Corresponding Linear Transfer Functions

Temperature Range

Maximum Deviation of Linear Equation

Linear Equation

from Parabolic Equation

TMIN (°C)

TMAX (°C)

(V)

(°C)

–55

+130

VOUT = –11.79mV/°C x T + 1.8528

±1.41

–40

+110

VOUT = –11.77mV/°C x T + 1.8577

±0.93

–30

+100

VOUT = –11.77mV/°C x T + 1.8605

±0.70

–40

+85

VOUT = –11.67mV/°C x T + 1.8583

±0.65

–10

+65

VOUT = –11.71mV/°C x T + 1.8641

±0.23

+35

+45

VOUT = –11.81mV/°C x T + 1.8701

±0.004

+20

+30

VOUT = –11.69mV/°C x T + 1.8663

±0.004

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