LM62CIM3X National Semiconductor, LM62CIM3X Datasheet - Page 5

• Manufacturer Part Number: LM62CIM3X
• Description: IC TEMP SENSOR 2.7V SOT23-3
• Manufacturer: National Semiconductor

Specifications of LM62CIM3X

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LM62CIM3X; LM62CIM3XTR

1.0 Mounting
The LM62 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or ce-
mented to a surface. The temperature that the LM62 is sens-
ing will be within about +0.2°C of the surface temperature that
LM62's leads are attached to.
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 measured would be at an intermediate temper-
ature between the surface temperature and the air tempera-
ture.
To ensure good thermal conductivity the backside of the
LM62 die is directly attached to the GND pin. The lands and
traces to the LM62 will, of course, be part of the printed circuit
board, which is the object whose temperature is being mea-
sured. These printed circuit board lands and traces will not
cause the LM62's temperature to deviate from the desired
temperature.
Alternatively, the LM62 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 LM62 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 ensure
that moisture cannot corrode the LM62 or its connections.
The thermal resistance junction to ambient (θ
rameter used to calculate the rise of a device junction tem-
perature due to its power dissipation. For the LM62 the
equation used to calculate the rise in the die temperature is
as follows:
where I
the output. Since the LM62's junction temperature is the ac-
tual temperature being measured care should be taken to
minimize the load current that the LM62 is required to drive.
The table shown in
perature of the LM62 without any loading, and the thermal
resistance for different conditions.
Still air
Moving air
T
J
= T
Q
is the quiescent current and I
A
+ θ
(°C/W)
JA
450
θ
no heat sink
[(+V
JA
Figure 3
(Note
SOT-23
S
I
Q
) + (+V
13)
T
J
0.17
(°C)
summarizes the rise in die tem-
− T
S
A
− V
O
L
(°C/W)
is the load current on
) I
260
180
θ
small heat fin
L
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]
(Note
SOT-23
JA
) is the pa-
12)
T
J
0.07
(°C)
0.1
− T
A
5
Note 12: Heat sink used is ½ square printed circuit board with 2 oz. foil with
part attached as shown in
Note 13: Part soldered to 30 gauge wire.
2.0 Capacitive Loads
The LM62 handles capacitive loading well. Without any spe-
cial precautions, the LM62 can drive any capacitive load as
shown in
LM62 has a maximum output impedance of 4.7 kΩ. In an ex-
tremely noisy environment it may be necessary to add some
filtering to minimize noise pickup. It is recommended that
0.1 μF be added from +V
voltage, as shown in
be necessary to add a capacitor from the output to ground. A
1 μF output capacitor with the 4.7 kΩ maximum output
impedance will form a 34 Hz lowpass filter. Since the thermal
time constant of the LM62 is much slower than the 30 ms time
constant formed by the RC, the overall response time of the
LM62 will not be significantly affected. For much larger ca-
pacitors this additional time lag will increase the overall re-
sponse time of the LM62.
FIGURE 4. LM62 No Decoupling Required for Capacitive
FIGURE 5. LM62 with Filter for Noisy Environment
FIGURE 3. Temperature Rise of LM62 Due to
Self-Heating and Thermal Resistance (θ
Figure
4. Over the specified temperature range the
Figure
Figure 2
S
to GND to bypass the power supply
Load
5. In a noisy environment it may
.
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)
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