LM45BIM3 National Semiconductor, LM45BIM3 Datasheet - Page 6

• Manufacturer Part Number: LM45BIM3
• Description: Temperature Sensor IC
• Manufacturer: National Semiconductor

Specifications of LM45BIM3

• Peak Reflow Compatible (260 C): No
• Ic Function: Temperature Sensor IC
• Supply Voltage Max: 10V
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Supply Voltage Min: 4.5V
• Operating Temperature Min: -20°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Printed Circuit Board
Applications
The LM45 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or
cemented to a surface and its temperature will be within
about 0.2˚C of the surface temperature.
This presumes that the ambient air temperature is almost the
same as the surface temperature; if the air temperature were
much higher or lower than the surface temperature, the
actual temperature of the LM45 die would be at an interme-
diate temperature between the surface temperature and the
air temperature.
To ensure good thermal conductivity the backside of the
LM45 die is directly attached to the GND pin. The lands and
traces to the LM45 will, of course, be part of the printed
circuit board, which is the object whose temperature is being
measured. These printed circuit board lands and traces will
not cause the LM45s temperature to deviate from the de-
sired temperature.
Alternatively, the LM45 can be mounted inside a sealed-end
metal tube, and can then be dipped into a bath or screwed
FIGURE 3. Printed Circuit Board Used for Heat Sink to Generate All Curves.
1
⁄
2
" Square Printed Circuit Board with 2 oz. Foil or Similar
6
into a threaded hole in a tank. As with any IC, the LM45 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 conden-
sation 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 LM45 or its connec-
tions.
Temperature Rise of LM45 Due to Self-Heating (Thermal
Resistance)
* Part soldered to 30 gauge wire.
** Heat sink used is
attached as shown in Figure 3.
Still air
Moving air
01175423
1
⁄
2
” square printed circuit board with 2 oz. foil with part
no heat sink*
SOT-23
450˚C/W
small heat fin**
SOT-23
260˚C/W
180˚C/W