LM75CIMM-3 National Semiconductor, LM75CIMM-3 Datasheet - Page 13

• Manufacturer Part Number: LM75CIMM-3
• Description: Temperature Sensor IC
• Manufacturer: National Semiconductor

Specifications of LM75CIMM-3

• Peak Reflow Compatible (260 C): No
• Ic Function: Temperature Sensor IC
• Supply Voltage Max: 5.5V
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Supply Voltage Min: 3V
• Operating Temperature Min: -55°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

3.0 Application Hints
To get the expected results when measuring temperature
with an integrated circuit temperature sensor like the LM75,
it is important to understand that the sensor measures its
own die temperature. For the LM75, the best thermal path
between the die and the outside world is through the LM75’s
pins. In the MSOP-8 package, the GND pin is directly con-
nected to the die, so the GND pin provides the best thermal
path. If the other pins are at different temperatures (unlikely,
but possible), they will affect the die temperature, but not as
strongly as the GND pin. In the SO-8 package, none of the
pins is directly connected to the die, so they will all contribute
similarly to the die temperature. Because the pins represent
a good thermal path to the LM75 die, the LM75 will provide
an accurate measurement of the temperature of the printed
4.0 Typical Applications
When using the two-wire interface: program O.S. for active high and connect O.S. directly to Q2’s gate.
FIGURE 9. Data Acquisition System with Temperature Input via I
FIGURE 8. Simple Fan Controller, Interface Optional
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circuit board on which it is mounted. There is a less efficient
thermal path between the plastic package and the LM75 die.
If the ambient air temperature is significantly different from
the printed circuit board temperature, it will have a small ef-
fect on the measured temperature.
In probe-type applications, the LM75 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
LM75 and accompanying wiring and circuits must be kept in-
sulated and dry, to avoid leakage and corrosion. This is es-
pecially 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 of-
ten used to insure that moisture cannot corrode the LM75 or
its connections.
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