sm72480sdx-125 National Semiconductor Corporation, sm72480sdx-125 Datasheet - Page 13

• Manufacturer Part Number: sm72480sdx-125
• Description: Solarmagic 1.6v, Llp-6 Factory Preset Temperature Switch And Temperature Sensor
• Manufacturer: National Semiconductor Corporation

4.3 VOLTAGE SHIFT
The SM72480 is very linear over temperature and supply
voltage range. Due to the intrinsic behavior of an NMOS/
PMOS rail-to-rail buffer, a slight shift in the output can occur
when the supply voltage is ramped over the operating range
of the device. The location of the shift is determined by the
relative levels of V
when V
This slight shift (a few millivolts) takes place over a wide
change (approximately 200 mV) in V
shift takes place over a wide temperature change of 5°C to
20°C, V
tions in the Electrical Characteristics table already includes
this possible shift.
FIGURE 2. SM72480 with series resistor for capacitive
FIGURE 1. SM72480 No Decoupling Required for
DD
TEMP
Capacitive Loads Less than 1100 pF.
− V
100 nF to 999 nF
is always monotonic. The accuracy specifica-
TEMP
1.1 nF to 99 nF
loading greater than 1100 pF.
C
= 1.0V.
DD
1 μF
LOAD
and V
TEMP
. The shift typically occurs
Minimum R
DD
1.5 kΩ
800 Ω
3 kΩ
or V
TEMP
S
. Since the
30142015
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13
5.0 Mounting and Temperature
Conductivity
The SM72480 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 best thermal conductivity between the device and the
PCB is achieved by soldering the DAP of the package to the
thermal pad on the PCB. The temperatures of the lands and
traces to the other leads of the SM72480 will also affect the
temperature reading.
Alternatively, the SM72480 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 SM72480
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. If moisture creates a short circuit from
the V
SM72480 will not be correct. Printed-circuit coatings are often
used to ensure that moisture cannot corrode the leads or cir-
cuit traces.
The thermal resistance junction-to-ambient (θ
rameter used to calculate the rise of a device junction tem-
perature due to its power dissipation. The equation used to
calculate the rise in the SM72480's die temperature is
where T
rent, I
voltage. For example, in an application where T
V
I
ing a self-heating error of only 0.021°C. Since the SM72480's
junction temperature is the actual temperature being mea-
sured, care should be taken to minimize the load current that
the V
put is used with a 100 k pull-up resistor, and this output is
asserted (low), then for this example the additional contribu-
tion is [(152° C/W)x(5V)
heating error of 0.059°C.
resistance of the SM72480.
L
DD
Device Number
= 2 μA, the junction temperature would be 30.021 °C, show-
SM72480SD
= 5 V, I
TEMP
TEMP
L
is the load current on the output, and V
A
FIGURE 3. SM72480 Thermal Resistance
is the ambient temperature, I
output to ground or V
output is required to drive. If The OVERTEMP out-
DD
= 9 μA, Gain 4, V
NS Package
2
Number
SDB06A
/100k] = 0.038°C for a total self-
Figure 3
DD
, the V
TEMP
Q
TEMP
shows the thermal
is the quiescent cur-
Resistance (θ
= 2231 mV, and
output from the
152° C/W
Thermal
O
JA
is the output
www.national.com
) is the pa-
A
= 30 °C,
JA
)