LM61CIM3/NOPB National Semiconductor, LM61CIM3/NOPB Datasheet - Page 6

• Manufacturer Part Number: LM61CIM3/NOPB
• Description: IC, TEMPERATURE SENSOR, ± 3°C, 3-SOT-23
• Manufacturer: National Semiconductor

Specifications of LM61CIM3/NOPB

• Ic Output Type: Voltage
• Sensing Accuracy Range: ± 3°C
• Supply Current: 82µA
• Supply Voltage Range: 2.7V To 10V
• Sensor Case Style: SOT-23
• No. Of Pins: 3
• Msl: MSL 1 - Unlimited
• Accuracy %: 3°C
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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1.0 Mounting
The LM61 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 LM61 is sens-
ing will be within about +0.2°C of the surface temperature that
LM61'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
LM61 die is directly attached to the GND pin. The lands and
traces to the LM61 will, of course, be part of the printed circuit
board, which is the object whose temperature is being mea-
sured.
Alternatively, the LM61 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 LM61 and
*Part soldered to 30 gauge wire.
**Heat sink used is ½ square printed circuit board with 2 oz. foil with part attached as shown in
***Part glued and leads soldered to 1" square of 1/16" printed circuit board with 2oz. foil or similar.
2.0 Capacitive Loads
The LM61 handles capacitive loading well. Without any spe-
cial precautions, the LM61 can drive any capacitive load as
shown in
LM61 has a maximum output impedance of 5 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 5 kΩ maximum output
impedance will form a 32 Hz lowpass filter. Since the thermal
time constant of the LM61 is much slower than the 5 ms time
constant formed by the RC, the overall response time of the
LM61 will not be significantly affected. For much larger ca-
pacitors this additional time lag will increase the overall re-
sponse time of the LM61.
FIGURE 4. LM61 No Decoupling Required for Capacitive
Still air
Moving air
Figure
4. Over the specified temperature range the
Figure
S
to GND to bypass the power supply
Load
(°C/W)
5. In a noisy environment it may
450
θ
no heat sink
JA
SOT-23*
T
FIGURE 3. Temperature Rise of LM61 Due to
J
0.26
(°C)
Self-Heating and Thermal Resistance (θ
− T
A
(°C/W)
260
180
θ
small heat fin
JA
1289715
SOT-23**
T
6
J
0.13
0.09
(°C)
− T
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 LM61 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 LM61 the
equation used to calculate the rise in the die temperature is
as follows:
where I
the output. Since the LM61's junction temperature is the ac-
tual temperature being measured care should be taken to
minimize the load current that the LM61 is required to drive.
The table shown in
perature of the LM61 without any loading with a 3.3V supply,
and the thermal resistance for different conditions.
A
FIGURE 5. LM61 with Filter for Noisy Environment
T
J
= T
Q
(°C/W)
180
θ
is the quiescent current and I
90
no heat sink
JA
A
+ θ
TO-92*
JA
JA
)
[(+V
T
Figure 3
J
0.09
0.05
(°C)
S
− T
I
Q
A
) + (+V
Figure
summarizes the rise in die tem-
(°C/W)
S
140
θ
70
small heat fin
− V
2.
JA
TO-92***
O
L
is the load current on
) I
L
]
T
J
0.07
0.03
(°C)
JA
− T
) is the pa-
A
1289716