TMP112 datasheet(18/24 Pages) TI

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USING THE SLOPE SPECIFICATIONS WITH A

Power-Supply Level Contribution to Accuracy

Accuracy

= (V

3.3V)

PSR

+0.250°C

(14)

Accuracy

= (1.8V

3.3V)

PSR

+0.250°C

=+0.375°C

0.8

0.6

0.4

0.2

0.4

0.6

Temperature( C)

Slope1

MAX

Slope2

MAX

Slope3

MAX

Calibrationat+25 CRemovesOffset

-40

-20

130

100 110 120

80 90

20 30

-30

-10

TMP112

SBOS473B – MARCH 2009 – REVISED JUNE 2009 ......................................................................................................................................................... www.ti.com

Using the previous example temperature range of

1-POINT CALIBRATION

0°C to +50°C, the worst-case temperature error is

now reduced to the worst-case slopes because the

The initial accuracy assurance at +25°C with the

offset at +25°C (that is, the maximum and minimum

slope regions provides an accuracy that is high

temperature errors of +0.3°C and –0.5°C) is removed.

enough for most applications; however, if higher

Therefore, a user can expect the worst-case accuracy

accuracy is desired, this increase can be achieved

to improve to +0.175°C.

with a 1-point calibration at +25°C. This calibration

removes the offset at room temperature, thereby

reducing

the

source

error

TMP112

temperature reading down to the curvature. Figure 20

The superior accuracy that can be achieved with the

shows the error of a calibrated TMP112.

TMP112 is complemented by its immunity to dc

variations from a 3.3V supply voltage. This immunity

is important because it spares the user from having to

use another LDO to produce 3.3V to achieve

accuracy. Nevertheless, the noise quantization that

results from changing supply can add some slight

change in temperature measurement accuracy. As an

example, if the user chooses to operate at 1.8V, the

worst-case expected change in accuracy can be

calculated by Equation 14:

(15)

This example is a worst-case accuracy contribution

Figure 20. Calibrated Accuracy and Slope Curves

as a result of variation in power supply that should be

versus Temperature

added to the accuracy + slope maximum.

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