LM71, LM71-Q1

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SNIS125D – MARCH 2004 – REVISED MARCH 2013

Application Hints

To get the expected results when measuring temperature with an integrated circuit temperature sensor like the

LM71, it is important to understand that the sensor measures its own die temperature. For the LM71, the best

thermal path between the die and the outside world is through the LM71's pins. In the SOT-23 package, all the

pins on the LM71 will have an equal effect on the die temperature. Because the pins represent a good thermal

path to the LM71 die, the LM71 will provide an accurate measurement of the temperature of the printed circuit

board on which it is mounted. There is a less efficient thermal path between the plastic package and the LM71

die. If the ambient air temperature is significantly different from the printed circuit board temperature, it will have

a small effect on the measured temperature.

In probe-type applications, the LM71 can be mounted inside a sealed-end metal tube, and can then be dipped

into a bath or screwed into a threaded hole in a tank. As with any IC, the LM71 and accompanying wiring and

circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may

operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as

Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM71 or its

connections.

Typical Applications

Figure 14. Temperature monitor using Intel 196 processor

Figure 15. LM71 digital input control using micro-controller's general purpose I/O.

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Product Folder Links: LM71 LM71-Q1