aSM121
- 3 -
© Andigilog, Inc. 2004
www.andigilog.com
July 2005 - 70A04006
25
Figure 1. aSM121 Output Voltage vs. Temperature
Mounting
The
aSM121
package
provides
good
thermal
conductivity to the surface to which it is soldered. It’s
low mass allows it to respond quickly to changes in
board temperature. In this case, its temperature will be
within about 0.02°C of the temperature of the surface it
is attached to if the ambient air temperature is almost
the same as the surface temperature. If the air
temperature is much higher or lower than the surface
temperature, the actual temperature of the aSM121
die will be at an intermediate temperature between the
surface temperature and the air temperature.
To ensure good thermal conductivity, the backside of
the aSM121 die is directly attached to the GND pin.
The lands and traces to the aSM121 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
aSM121’s temperature to deviate from the desired
temperature.
Alternatively, the aSM121 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 aSM121 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
condensation can occur. Printed-circuit coatings and
varnishes such as Humiseal and epoxy paint or dips
can be used to ensure that moisture cannot corrode
the aSM121 or its connections.
50
75
100
125
-30
0
1750
200
750
500
V
OUT (mV)
Temperature (ºC)
1500
Temp (ºC) = (V
OUT – 500mV) / 10mV/ºC)
900
1350
300
25
75
100
125
-30
50
0
1750
200
750
500
V
OUT (mV)
Temperature (ºC)
1500
Temp (ºC) = (V
OUT – 500mV) / 10mV/ºC)
900
1350
300
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