LM35 Datasheet, PDF (8/15 Pages) National Semiconductor (TI) – Precision Centigrade Temperature Sensors

Typical Applications
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FIGURE 3. LM35 with Decoupling from Capacitive Load
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FIGURE 4. LM35 with R-C Damper
CAPACITIVE LOADS
Like most micropower circuits, the LM35 has a limited ability
to drive heavy capacitive loads. The LM35 by itself is able to
drive 50 pf without special precautions. If heavier loads are
anticipated, it is easy to isolate or decouple the load with a
resistor; see Figure 3. Or you can improve the tolerance of
capacitance with a series R-C damper from output to
ground; see Figure 4.
When the LM35 is applied with a 200Ω load resistor as
shown in Figure 5, Figure 6 or Figure 8 it is relatively immune
to wiring capacitance because the capacitance forms a by-
pass from ground to input, not on the output. However, as
with any linear circuit connected to wires in a hostile envi-
ronment, its performance can be affected adversely by in-
tense electromagnetic sources such as relays, radio trans-
mitters, motors with arcing brushes, SCR transients, etc, as
its wiring can act as a receiving antenna and its internal
junctions can act as rectifiers. For best results in such cases,
a bypass capacitor from V_IN to ground and a series R-C
damper such as 75Ω in series with 0.2 or 1 µF from output to
ground are often useful. These are shown in Figure 13,
Figure 14, and Figure 16.
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FIGURE 6. Two-Wire Remote Temperature Sensor
(Output Referred to Ground)
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FIGURE 7. Temperature Sensor, Single Supply, −55˚ to
+150˚C
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FIGURE 8. Two-Wire Remote Temperature Sensor
(Output Referred to Ground)
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FIGURE 5. Two-Wire Remote Temperature Sensor
(Grounded Sensor)
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FIGURE 9. 4-To-20 mA Current Source (0˚C to +100˚C)
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