3.0 Application Hints

3.1 THERMAL PATH CONSIDERATIONS

To get the expected results when measuring temperature

with an integrated circuit temperature sensor like the LM73,

it is important to understand that the sensor measures its

own die temperature. For the LM73, the best thermal path

between the die and the outside world is through the LM73’s

pins. In the SOT23 package, all the pins on the LM73 will

have an equal effect on the die temperature. Because the

pins represent a good thermal path to the LM73 die, the

LM73 will provide an accurate measurement of the tempera-

ture of the printed circuit board on which it is mounted. There

is a less efficient thermal path between the plastic package

and the LM73 die. If the ambient air temperature is signifi-

cantly different from the printed circuit board temperature, it

will have a small effect on the measured temperature.

3.2 OUTPUT CONSIDERATIONS: TIGHT ACCURACY,

RESOLUTION AND LOW NOISE

The LM73 is well suited for applications that require tight

temperature measurement accuracy. In many applications,

the low temperature error can mean better system perfor-

mance and, by eliminating a system calibration step, lower

production cost.

With digital resolution as fine as 0.03125 ˚C/LSB, the LM73

senses and reports very small changes in its temperature,

making it ideal for applications where temperature sensitivity

is important. For example, the LM73 enables the system to

quickly identify the direction of temperature change, allowing

the processor to take compensating action before the sys-

tem reaches a critical temperature.

The LM73 has very low output noise, typically 0.015˚C rms,

which makes it ideal for applications where stable thermal

compensation is a priority. For example, in a temperature-

compensated oscillator application, the very small deviation

in successive temperature readings translates to a stable

frequency output from the oscillator.

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