Datasheet
USING THE SLOPE SPECIFICATIONS WITH A
Power-Supply Level Contribution to Accuracy
Accuracy = (V 3.3V)± - ´
PSR S
+0.250°C
V
(14)
Accuracy = (1.8V 3.3V)± - ´
PSR
+0.250°C
V
=+0.375°C
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
-
-
-
TemperatureError( C)
°
Temperature( C)°
Slope1
MAX
Slope2
MAX
Slope3
MAX
Calibrationat+25 CRemovesOffset°
-40 -20 0 40 60 130100 110 12080 90705020 3010-30 -10
TMP112
SBOS473B – MARCH 2009 – REVISED JUNE 2009 .........................................................................................................................................................
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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 of error in a 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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