LM20
2.4V, 10µA, SC70, micro SMD Temperature Sensor
General Description
The LM20 is a precision analog output CMOS integratedcircuit 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 LM20 is
predominately linear, yet has a slight predictable parabolic
curvature. The accuracy of the LM20 when specified to a
parabolic transfer function is
ture of +30˚C. The temperature error increases linearly and
reaches a maximum of
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 LM20’s quiescent current is less than 10 µA. Therefore,
self-heating is less than 0.02˚C in still air. Shutdown capability for the LM20 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.
±
1.5˚C at an ambient tempera-
±
2.5˚C at the temperature range
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 an SC70 and a micro SMD 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 +2.4V to +5.5V
j
Current Drain 10 µA (max)
j
Nonlinearity
j
Output Impedance 160 Ω (max)
j
Load Regulation
<
<
I
0µA
+16 µA −2.5 mV (max)
L
±
1.5 to±4 ˚C (max)
±
2.5 to±5 ˚C (max)
March 2004
±
0.4 % (typ)
LM20 2.4V, 10µA, SC70, micro SMD Temperature Sensor
Typical Application
Full-Range Celsius (Centigrade) Temperature Sensor (−55˚C to +130˚C)
Operating from a Single Li-Ion Battery Cell
VO= (−3.88x10−6xT2) + (−1.15x10−2xT) + 1.8639
where:
T is temperature, and V
is the measured output voltage of the LM20.
O
10090802
Output Voltage vs Temperature
10090824
© 2004 National Semiconductor Corporation DS100908 www.national.com
Typical Application (Continued)
LM20
Connection Diagrams
SC70-5 micro SMD
Temperature (T) Typical V
+130˚C +303 mV
+100˚C +675 mV
+80˚C +919 mV
+30˚C +1515 mV
+25˚C +1574 mV
0˚C +1863.9 mV
−30˚C +2205 mV
−40˚C +2318 mV
−55˚C +2485 mV
O
Note:
- GND (pin 2) may be grounded or left floating. For optimum thermal
conductivity to the pc board ground plane pin 2 should be grounded.
- NC (pin 1) should be left floating or grounded. Other signal traces
should not be connected to this pin.
Top View
See NS Package Number MAA05A
10090801
Note:
- Pin numbers are referenced to the package marking text orientation.
- Reference JEDEC Registration MO-211, variation BA
- The actual physical placement of package marking will vary slightly from
part to part. The package marking will designate the date code and will vary
considerably. Package marking does not correlate to device type in any way.
Top View
See NS Package Number BPA04DDC and TLA04ZZA
Ordering Information
Order Temperature Temperature NS Package Device
Number Accuracy Range Number Marking Transport Media
LM20BIM7
LM20BIM7X
LM20CIM7
LM20CIM7X
LM20SIBP
LM20SIBPX
LM20SITL
LM20SITLX
±
2.5˚C −55˚C to +130˚C MAA05A T2B 1000 Units on Tape and Reel
±
2.5˚C −55˚C to +130˚C MAA05A T2B 3000 Units on Tape and Reel
±
5˚C −55˚C to +130˚C MAA05A T2C 1000 Units on Tape and Reel
±
5˚C −55˚C to +130˚C MAA05A T2C 3000 Units on Tape and Reel
±
3.5˚C −40˚C to +125˚C BPA04DDC Date
250 Units on Tape and Reel
Code
±
3.5˚C −40˚C to +125˚C BPA04DDC Date
3000 Units on Tape and Reel
Code
±
3.5˚C −40˚C to +125˚C TLA04ZZA Date
250 Units on Tape and Reel
Code
±
3.5˚C −40˚C to +125˚C TLA04ZZA Date
3000 Units on Tape and Reel
Code
10090832
www.national.com 2
LM20
Absolute Maximum Ratings (Note 1)
Supply Voltage +6.5V to −0.2V
Output Voltage (V
Output Current 10 mA
Input Current at any pin (Note 2) 5 mA
Storage Temperature −65˚C to
Maximum Junction Temperature
(T
) +150˚C
JMAX
ESD Susceptibility (Note 3) :
Human Body Model 2500 V
Machine Model 250 V
Soldering process must comply with National’s
+
+ 0.6 V) to
−0.6 V
+150˚C
Operating Ratings(Note 1)
Specified Temperature Range: T
LM20B, LM20C with
+
2.4 V ≤ V
≤ 2.7 V −30˚C ≤ TA≤ +130˚C
LM20B, LM20C with
+
2.7 V ≤ V
≤ 5.5 V −55˚C ≤ TA≤ +130˚C
LM20S with
+
2.4 V ≤ V
≤ 5.5 V −30˚C ≤ TA≤ +125˚C
LM20S with
2.7 V ≤ V+≤ 5.5 V −40˚C ≤ TA≤ +125˚C
Supply Voltage Range (V
Thermal Resistance, θ
+
) +2.4 V to +5.5 V
(Note 5)
JA
SC-70
micro SMD
MIN
≤ TA≤ T
MAX
415˚C/W
340˚C/W
Reflow Temperature Profile specifications. Refer to
www.national.com/packaging. (Note 4)
Electrical Characteristics
Unless otherwise noted, these specifications apply for V+= +2.7 VDC. Boldface limits apply for TA=TJ=T
other limits T
Parameter Conditions Typical
= 25˚C; Unless otherwise noted.
A=TJ
(Note 6)
LM20B LM20C LM20S Units
Limits Limits Limits
(Note 7) (Note 7) (Note 7)
Temperature to Voltage Error
= (−3.88x10−6xT2)
V
O
+ (−1.15x10
−2
xT) + 1.8639V
(Note 8)
= +25˚C to +30˚C
T
A
T
= +130˚C
A
T
= +125˚C
A
T
= +100˚C
A
T
= +85˚C
A
T
= +80˚C
A
T
= 0˚C
A
T
= −30˚C
A
T
= −40˚C
A
T
= −55˚C
A
±
1.5
±
2.5
±
2.5
±
2.2
±
2.1
±
2.0
±
1.9
±
2.2
±
2.3
±
2.5
±
4.0
±
5.0 ˚C (max)
±
5.0
±
4.7
±
4.6
±
4.5
±
4.4
±
4.7
±
4.8
±
5.0 ˚C (max)
±
2.5 ˚C (max)
±
3.5 ˚C (max)
±
3.2 ˚C (max)
±
3.1 ˚C (max)
±
3.0 ˚C (max)
±
2.9 ˚C (max)
±
3.3 ˚C (min)
±
3.5 ˚C (max)
Output Voltage at 0˚C +1.8639 V
Variance from Curve
Non-Linearity (Note 9) −20˚C ≤ T
Sensor Gain (Temperature
−30˚C ≤ T
Sensitivity or Average Slope)
≤ +80˚C
A
≤ +100˚C −11.77 −11.4
A
±
1.0 ˚C
±
0.4 %
−12.2
−11.0
−12.6
−11.0
−12.6
to equation:
=−11.77 mV/˚CxT+1.860V
V
O
Output Impedance 0 µA ≤ I
≤ +16 µA
L
160 160 160 Ω (max)
(Notes 11, 12)
Load Regulation(Note 10) 0 µA ≤ IL≤ +16 µA
−2.5 −2.5 −2.5 mV (max)
(Notes 11, 12)
+
Line Regulation +2. 4 V ≤ V
+5.0 V ≤ V
Quiescent Current +2. 4V ≤ V
+5.0V ≤ V
+2. 4V ≤ V
Change of Quiescent Current +2. 4 V ≤ V
≤ +5.0V +3.3 +3.7 +3.7 mV/V (max)
+
≤ +5.5 V +11 +11 +11 mV (max)
+
≤ +5.0V 4.5 7 7 7 µA (max)
+
≤ +5.5V 4.5 9 9 9 µA (max)
+
≤ +5.0V 4.5 10 10 10 µA (max)
+
≤ +5.5V +0.7 µA
Temperature Coefficient of −11 nA/˚C
Quiescent Current
Shutdown Current V
+
≤ +0.8 V 0.02 µA
to T
MIN
mV/˚C (min)
mV/˚C (max)
MAX
(Limit)
; all
www.national.com3
Electrical Characteristics (Continued)
LM20
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: When the input voltage (V
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin.
Note 4: Reflow temperature profiles are different for lead-free and non-lead-free packages.
Note 5: The junction to ambient thermal resistance (θ
Note 6: Typicals are at T
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 8: Accuracy is defined as the error between the measured and calculated output voltage at the specified conditions of voltage, current, and temperature
(expressed in˚C).
Note 9: Non-Linearity is defined as the deviation of the calculated output-voltage-versus-temperature curve from the best-fit straight line, over the temperature
range specified.
Note 10: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating effects can be
computed by multiplying the internal dissipation by the thermal resistance.
Note 11: Negative currents are flowing into the LM20. Positive currents are flowing out of the LM20. Using this convention the LM20 can at most sink −1 µA and
source +16 µA.
Note 12: Load regulation or output impedance specifications apply over the supply voltage range of +2.4V to +5.5V.
Note 13: Line regulation is calculated by subtracting the output voltage at the highest supply input voltage from the output voltage at the lowest supply input voltage.
) at any pin exceeds power supplies (V
I
) is specified without a heat sink in still air using the printed circuit board layout shown in Figure 1.
= 25˚C and represent most likely parametric norm.
J=TA
JA
<
I
GND or V
>
V+), the current at that pin should be limited to 5 mA.
I
Typical Performance Characteristics
Temperature Error vs Temperature
PCB Layouts Used for Thermal Measurements
a) Layout used for no heat sink measurements.
10090829
FIGURE 1. PCB Lyouts used for thermal measurements.
1.0 LM20 Transfer Function
The LM20’s transfer function can be described in different
ways with varying levels of precision. A simple linear transfer
function, with good accuracy near 25˚C, is
= −11.69 mV/˚C x T + 1.8663 V
V
O
www.national.com 4
b) Layout used for measurements with small heat hink.
Over the full operating temperature range of −55˚C to
+130˚C, best accuracy can be obtained by using the parabolic transfer function
solving for T:
10090825
10090830
= (−3.88x10−6xT2) + (−1.15x10−2xT) + 1.8639
V
O
1.0 LM20 Transfer Function
(Continued)
A linear transfer function can be used over a limited temperature range by calculating a slope and offset that give best
results over that range. A linear transfer function can be
calculated from the parabolic transfer function of the LM20.
The slope of the linear transfer function can be calculated
using the following equation:
m = −7.76 x 10
where T is the middle of the temperature range of interest
and m is in V/˚C. For example for the temperature range of
T
min
=−30 to T
=+100˚C:
max
−6
T=35˚C
x T − 0.0115,
and
m = −11.77 mV/˚C
The offset of the linear transfer function can be calculated
using the following equation:
b=(V
)+VOP(T)+mx(T
OP(Tmax
max
+T))/2
,
where:
VOP(T
•
the parabolic transfer function for V
VOP(T) is the calculated output voltage at T using the
•
parabolic transfer function for V
) is the calculated output voltage at T
max
O
.
O
max
using
Using this procedure the best fit linear transfer function for
many popular temperature ranges was calculated in Figure
2. As shown in Figure 2 the error that is introduced by the
linear transfer function increases with wider temperature
ranges.
LM20
Temperature Range Linear Equation
(˚C) T
T
min
max
(˚C)
V
−55 +130 −11.79 mV/˚C x T + 1.8528 V
−40 +110 −11.77 mV/˚C x T + 1.8577 V
−30 +100 −11.77 mV/˚C x T + 1.8605 V
-40 +85 −11.67 mV/˚C x T + 1.8583 V
−10 +65 −11.71 mV/˚C x T + 1.8641 V
+35 +45 −11.81 mV/˚C x T + 1.8701 V
+20 +30 −11.69 mV/˚C x T + 1.8663 V
FIGURE 2. First order equations optimized for different temperature ranges.
2.0 Mounting
The LM20 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 LM20 is
sensing will be within about +0.02˚C of the surface temperature to which the LM20’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
temperature between the surface temperature and the air
temperature.
To ensure good thermal conductivity the backside of the
LM20 die is directly attached to the pin 2 GND pin. The
tempertures of the lands and traces to the other leads of the
LM20 will also affect the temperature that is being sensed.
Alternatively, the LM20 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 LM20 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 paints or dips are often used to
ensure that moisture cannot corrode the LM20 or its connections.
The thermal resistance junction to ambient (θ
rameter used to calculate the rise of a device junction tem-
) is the pa-
JA
Maximum Deviation of Linear Equation
=
O
from Parabolic Equation (˚C)
±
1.41
±
0.93
±
0.70
±
0.65
±
0.23
±
0.004
±
0.004
perature due to its power dissipation. For the LM20 the
equation used to calculate the rise in the die temperature is
as follows:
T
where I
+ θJA[(V+IQ)+(V+−VO)IL]
J=TA
is the quiescent current and ILis the load current on
Q
the output. Since the LM20’s junction temperature is the
actual temperature being measured care should be taken to
minimize the load current that the LM20 is required to drive.
The tables shown in Figure 3 summarize the rise in die
temperature of the LM20 without any loading, and the thermal resistance for different conditions.
www.national.com5
2.0 Mounting (Continued)
LM20
SC70-5 SC70-5
no heat sink small heat sink
θ
JA
TJ−T
A
(˚C/W) (˚C) (˚C/W) (˚C)
Still air 412 0.2 350 0.19
Moving air 312 0.17 266 0.15
See Figure 1 for PCB layout samples.
micro SMD micro SMD
no heat sink small heat fin
θ
JA
TJ−T
A
(˚C/W) (˚C) (˚C/W) (˚C)
Still air 340 0.18 TBD TBD
Moving air TBD TBD TBD TBD
300 pF as shown in Figure 4. Over the specified temperature
range the LM20 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 recommended that 0.1 µF be added from V
+
to GND to bypass the
power supply voltage, as shown in Figure 5. In a noisy
θ
JA
TJ−T
A
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
LM20 is much slower, the overall response time of the LM20
will not be significantly affected.
θ
JA
TJ−T
A
10090815
FIGURE 3. Temperature Rise of LM20 Due to
Self-Heating and Thermal Resistance (θ
JA
)
FIGURE 4. LM20 No Decoupling Required for
Capacitive Loads Less than 300 pF.
3.0 Capacitive Loads
The LM20 handles capacitive loading well. Without any precautions, the LM20 can drive any capacitive load less than
R(Ω) C (µF)
200 1
470 0.1
680 0.01
1 k 0.001
10090816 10090833
FIGURE 5. LM20 with Filter for Noisy Environment and Capacitive Loading greater than 300 pF. Either placement of
resistor as shown above is just as effective.
4.0 LM20 micro SMD Light Sensitivity
Exposing the LM20 micro SMD package to bright sunlight
may cause the output reading of the LM20 to drop by 1.5V. In
a normal office environment of fluorescent lighting the output
voltage is minimally affected (less than a millivolt drop). In
www.national.com 6
either case it is recommended that the LM20 micro SMD be
placed inside an enclosure of some type that minimizes its
light exposure. Most chassis provide more than ample protection. The LM20 does not sustain permanent damage from
light exposure. Removing the light source will cause LM20’s
output voltage to recover to the proper value.
5.0 Applications Circuits
LM20
10090818
FIGURE 6. Centigrade Thermostat
10090819
FIGURE 7. Conserving Power Dissipation with Shutdown
10090828
Most CMOS ADCs found in ASICs have a sampled data comparator input structure that is notorious for causing grief to analog
output devices such as the LM20 and many op amps. The cause of this grief is the requirement of instantaneous charge of the
input sampling capacitor in the ADC. This requirement is easily accommodated by the addition of a capacitor. Since not all ADCs
have identical input stages, the charge requirements will vary necessitating a different value of compensating capacitor. This ADC
is shown as an example only. If a digital output temperature is required please refer to devices such as the LM74.
FIGURE 8. Suggested Connection to a Sampling Analog to Digital Converter Input Stage
www.national.com7
Physical Dimensions inches (millimeters) unless otherwise noted
LM20
5-Lead SC70 Molded Package
Order Number LM20BIM7 or LM20CIM7X
NS Package Number MAA05A
4-Bump micro SMD Ball Grid Array Package (Small Bump)
Order Number LM20SIBP or LM20SIBPX
NS Package Number BPA04DDC
The following dimensions apply to the BPA04DDC package
shown above: X1=X2 = 853µm
www.national.com 8
±
30µm, X3= 900µm±50µm
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LM20 2.4V, 10µA, SC70, micro SMD Temperature Sensor
4-Bump micro SMD Ball Grid Array Package (Large Bump)
Order Number LM20SITL or LM20SITLX
NS Package Number TLA04ZZA
The following dimensions apply to the TLA04ZZA package
±
shown above: X1=X2 = 963µm
30µm, X3= 600µm±75µm
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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