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PDF LM19CIZ Data sheet ( Hoja de datos )
| Número de pieza | LM19CIZ | |
| Descripción | 2.4V/ 10uA/ TO-92 Temperature Sensor | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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January 2003
LM19
2.4V, 10µA, TO-92 Temperature Sensor
General Description
The LM19 is a precision analog output CMOS integrated-
circuit temperature sensor that operates over a −55˚C to
+130˚C temperature range. The power supply operating
range is +2.4 V to +5.5 V. The transfer function of LM19 is
predominately linear, yet has a slight predictable parabolic
curvature. The accuracy of the LM19 when specified to a
parabolic transfer function is ±2.5˚C at an ambient tempera-
ture of +30˚C. The temperature error increases linearly and
reaches a maximum of ±3.8˚C at the temperature range
extremes. The temperature range is affected by the power
supply voltage. At a power supply voltage of 2.7 V to 5.5 V
the temperature range extremes are +130˚C and −55˚C.
Decreasing the power supply voltage to 2.4 V changes the
negative extreme to −30˚C, while the positive remains at
+130˚C.
The LM19’s quiescent current is less than 10 µA. Therefore,
self-heating is less than 0.02˚C in still air. Shutdown capa-
bility for the LM19 is intrinsic because its inherent low power
consumption allows it to be powered directly from the output
of many logic gates or does not necessitate shutdown at all.
Applications
n Cellular Phones
n Computers
n Power Supply Modules
n Battery Management
n FAX Machines
n Printers
n HVAC
n Disk Drives
n Appliances
Features
n Rated for full −55˚C to +130˚C range
n Available in a TO-92 package
n Predictable curvature error
n Suitable for remote applications
Key Specifications
j Accuracy at +30˚C
j Accuracy at +130˚C & −55˚C
j Power Supply Voltage Range
j Current Drain
j Nonlinearity
j Output Impedance
j Load Regulation
0 µA < IL< +16 µA
±2.5 ˚C (max)
±3.5 to ±3.8 ˚C (max)
+2.4V to +5.5V
10 µA (max)
±0.4 % (typ)
160 Ω (max)
−2.5 mV (max)
Typical Application
Output Voltage vs Temperature
20004002
VO = (−3.88x10−6xT2) + (−1.15x10−2xT) + 1.8639
or
20004024
where:
T is temperature, and VO is the measured output voltage of the LM19.
FIGURE 1. Full-Range Celsius (Centigrade) Temperature Sensor (−55˚C to +130˚C)
Operating from a Single Li-Ion Battery Cell
© 2003 National Semiconductor Corporation DS200040
www.national.com
1 page  
1.0 LM19 Transfer Function (Continued)
Temperature Range
Tmin (˚C)
−55
Tmax (˚C)
+130
−40 +110
−30 +100
-40 +85
−10 +65
+35 +45
+20 +30
Linear Equation
VO=
−11.79 mV/˚C x T + 1.8528 V
−11.77 mV/˚C x T + 1.8577 V
−11.77 mV/˚C x T + 1.8605 V
−11.67 mV/˚C x T + 1.8583 V
−11.71 mV/˚C x T + 1.8641 V
−11.81 mV/˚C x T + 1.8701 V
−11.69 mV/˚C x T + 1.8663 V
Maximum Deviation of Linear Equation
from Parabolic Equation (˚C)
±1.41
±0.93
±0.70
±0.65
±0.23
±0.004
±0.004
FIGURE 2. First Order Equations Optimized For Different Temperature Ranges.
2.0 Mounting
The LM19 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or
cemented to a surface. The temperature that the LM19 is
sensing will be within about +0.02˚C of the surface tempera-
ture to which the LM19’s leads are attached.
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
temperature between the surface temperature and the air
temperature.
To ensure good thermal conductivity the backside of the
LM19 die is directly attached to the GND pin. The temper-
tures of the lands and traces to the other leads of the LM19
will also affect the temperature that is being sensed.
Alternatively, the LM19 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 LM19 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 LM19 or its connec-
tions.
The thermal resistance junction to ambient (θJA) is the pa-
rameter used to calculate the rise of a device junction tem-
perature due to its power dissipation. For the LM19 the
equation used to calculate the rise in the die temperature is
as follows:
TJ = TA + θJA [(V+ IQ) + (V+ − VO) IL]
where IQ is the quiescent current and ILis the load current on
the output. Since the LM19’s junction temperature is the
actual temperature being measured care should be taken to
minimize the load current that the LM19 is required to drive.
The tables shown in Figure 3 summarize the rise in die
temperature of the LM19 without any loading, and the ther-
mal resistance for different conditions.
Still air
Moving air
TO-92
no heat sink
θJA
(˚C/W)
TJ − TA
(˚C)
150 TBD
TBD
TBD
TO-92
small heat fin
θJA
(˚C/W)
TJ − TA
(˚C)
TBD
TBD
TBD
TBD
FIGURE 3. Temperature Rise of LM19 Due to
Self-Heating and Thermal Resistance (θJA)
3.0 Capacitive Loads
The LM19 handles capacitive loading well. Without any pre-
cautions, the LM19 can drive any capacitive load less than
300 pF as shown in Figure 4. Over the specified temperature
range the LM19 has a maximum output impedance of 160 Ω.
In an extremely noisy environment it may be necessary to
add some filtering to minimize noise pickup. It is recom-
mended that 0.1 µF be added from V+ to GND to bypass the
power supply voltage, as shown in Figure 5. In a noisy
environment it may even be necessary to add a capacitor
from the output to ground with a series resistor as shown in
Figure 5. A 1 µF output capacitor with the 160 Ω maximum
output impedance and a 200 Ω series resistor will form a 442
Hz lowpass filter. Since the thermal time constant of the
LM19 is much slower, the overall response time of the LM19
will not be significantly affected.
20004015
FIGURE 4. LM19 No Decoupling Required for
Capacitive Loads Less than 300 pF.
5 www.national.com
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