SM73710 Datasheet, PDF (7/12 Pages) Texas Instruments – SM73710 2.7V, SOT-23 Temperature Sensor

30159814
FIGURE 2. Printed Circuit Board Used
for Heat Sink to Generate All Curves.
½″ Square Printed Circuit Board
with 2 oz. Copper Foil or Similar.
1.0 Mounting
The SM73710 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 SM73710 is
sensing will be within about +0.1°C of the surface temperature
that SM73710'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 of the SM73710 die would be at an intermediate
temperature between the surface temperature and the air
temperature.
To ensure good thermal conductivity the backside of the
SM73710 die is directly attached to the GND pin. The lands
and traces to the SM73710 will, of course, be part of the print-
ed circuit board, which is the object whose temperature is
being measured. These printed circuit board lands and traces
will not cause the SM73710's temperature to deviate from the
desired temperature.
Alternatively, the SM73710 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 SM73710
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 con-
densation 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 SM73710 or its con-
nections.
The thermal resistance junction to ambient (θ_JA ) is the pa-
rameter used to calculate the rise of a device junction tem-
perature due to the device power dissipation. For the
SM73710 the equation used to calculate the rise in the die
temperature is as follows:
T_J = T_A + θ _JA [(+V_S I_Q) + (+V_S − V_O) I_L]
where I_Q is the quiescent current and I_Lis the load current on
the output.
The table shown in Figure 3 summarizes the rise in die tem-
perature of the SM73710 without any loading, and the thermal
resistance for different conditions.
SOT-23*
no heat sink
SOT-23**
small heat fin
Still air
Moving air
θ _JA
(°C/W)
450
T _J − T_A
(°C)
0.17
θ _JA
(°C/W)
260
180
T _J − T_A
(°C)
0.1
0.07
*-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 Figure 2 .
FIGURE 3. Temperature Rise of SM73710 Due to
Self-Heating and Thermal Resistance (θ_JA)
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