LM20 2.

4V, 10µA, SC70, micro SMD Temperature Sensor

October 1999

LM20
2.4V, 10µA, SC70, micro SMD Temperature Sensor
General Description n Battery Management
n FAX Machines
The LM20 is a precision analog output CMOS
n Printers
integrated-circuit temperature sensor that operates over a
−55˚C to +130˚C temperature range. The power supply op- n HVAC
erating range is +2.4 V to +5.5 V. The transfer function of n Disk Drives
LM20 is predominately linear, yet has a slight predictable n Appliances
parabolic curvature. The accuracy of the LM20 when speci-
fied to a parabolic transfer function is ± 1.5˚C at an ambient Features
temperature of +30˚C. The temperature error increases lin-
n Rated for full −55˚C to +130˚C range
early and reaches a maximum of ± 2.5˚C at the temperature
n Available in an SC70 and a micro SMD package
range extremes. The temperature range is affected by the
power supply voltage. At a power supply voltage of 2.7 V to n Predictable curvature error
5.5 V the temperature range extremes are +130˚C and n Suitable for remote applications
−55˚C. Decreasing the power supply voltage to 2.4 V
changes the negative extreme to −30˚C, while the positive Key Specifications
remains at +130˚C.
n Accuracy at +30˚C ± 1.5 to ± 4 ˚C (max)
The LM20’s quiescent current is less than 10 µA. Therefore,
self-heating is less than 0.02˚C in still air. Shutdown capabil- n Accuracy at +130˚C & −55˚C ± 2.5 to ± 5 ˚C (max)
ity for the LM20 is intrinsic because its inherent low power n Power Supply Voltage Range +2.4V to +5.5V
consumption allows it to be powered directly from the output
n Current Drain 10 µA (max)
of many logic gates or does not necessitate shutdown at all.
n Nonlinearity ± 0.4 % (typ)
Applications n Output Impedance 160 Ω (max)
n Cellular Phones n Load Regulation
n Computers 0 µA < IL < +16 µA −2.5 mV (max)
n Power Supply Modules

Typical Application

Output Voltage vs Temperature

DS100908-2

VO = (−3.88x10−6xT2) + (−1.15x10−2xT) + 1.8639

or

where:
T is temperature, and VO is the measured output voltage of the LM20.

DS100908-24

Full-Range Celsius (Centigrade) Temperature Sensor (−55˚C to +130˚C)

Operating from a Single Li-Ion Battery Cell

© 1999 National Semiconductor Corporation DS100908 www.national.com

LM20
Typical Application (Continued) Temperature (T) Typical VO
+25˚C +1574 mV
Temperature (T) Typical VO 0˚C +1863.9 mV
+130˚C +303 mV −30˚C +2205 mV
+100˚C +675 mV −40˚C +2318 mV
+80˚C +919 mV −55˚C +2485 mV
+30˚C +1515 mV

Connection Diagrams

SC70-5 micro SMD

DS100908-1

Note:
DS100908-32
- GND (pin 2) may be grounded or left floating. For optimum thermal
conductivity to the pc board ground plane pin 2 should be grounded. Note:
- NC (pin 1) should be left floating or grounded. Other signal traces - Pin numbers are referenced to the package marking text orientation.
should not be connected to this pin. - Reference JEDEC Registration MO-211, variation BA
Top View - The actual physical placement of package marking will vary slightly
from part to part. The package marking will designate the date code and
See NS Package Number MAA05A will vary considerably. Package marking does not correlate to device type
in any way.
Top View
See NS Package Number BPA04DDC

Ordering Information
Order Temperature Temperature NS Package Device
Number Accuracy Range Number Marking Transport Media
LM20BIM7 ± 2.5˚C −55˚C to +130˚C MAA05A T2B 1000 Units on Tape and Reel
LM20BIM7X ± 2.5˚C −55˚C to +130˚C MAA05A T2B 3000 Units on Tape and Reel
LM20CIM7 ± 5˚C −55˚C to +130˚C MAA05A T2C 1000 Units on Tape and Reel
LM20CIM7X ± 5˚C −55˚C to +130˚C MAA05A T2C 3000 Units on Tape and Reel
LM20SIBP ± 3.5˚C −40˚C to +125˚C BPA04DDC Date 250 Units on Tape and Reel
Code
LM20SIBPX ± 3.5˚C −40˚C to +125˚C BPA04DDC Date 3000 Units on Tape and Reel
Code

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 LM20
Absolute Maximum Ratings (Note 1) Lead Temperature
SC-70 Package (Note 4) :
Supply Voltage +6.5V to −0.2V
Vapor Phase (60 seconds) +215˚C
Output Voltage (V+ + 0.6 V) to
−0.6 V Infrared (15 seconds) +220˚C
Output Current 10 mA
Input Current at any pin (Note 2) 5 mA Operating Ratings(Note 1)
Storage Temperature −65˚C to +150˚C Specified Temperature Range: TMIN ≤ TA ≤ TMAX
Maximum Junction Temperature (TJMAX) +150˚C LM20B, LM20C with
ESD Susceptibility (Note 3) : 2.4 V ≤ V+≤ 2.7 V −30˚C ≤ TA ≤ +130˚C
Human Body Model 2500 V LM20B, LM20C with
2.7 V ≤ V+≤ 5.5 V −55˚C ≤ TA ≤ +130˚C
Machine Model 250 V
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+) +2.4 V to +5.5 V
Thermal Resistance, θJA(Note 5)
SC-70 415˚C/W
micro SMD TBD˚C/W

Electrical Characteristics
Unless otherwise noted, these specifications apply for V+ = +2.7 VDC. Boldface limits apply for TA = TJ = TMIN to TMAX ; all
other limits TA = TJ = 25˚C; Unless otherwise noted.
Parameter Conditions Typical LM20B LM20C LM20S Units
(Note 6) Limits Limits Limits (Limit)
(Note 7) (Note 7) (Note 7)
Temperature to Voltage Error TA = +25˚C to +30˚C ± 1.5 ± 4.0 ± 2.5 ˚C (max)
VO = (−3.88x10−6xT2) TA = +130˚C ± 2.5 ± 5.0 ˚C (max)
+ (−1.15x10−2xT) + 1.8639V TA = +125˚C ± 2.5 ± 5.0 ± 3.5 ˚C (max)
(Note 8)
TA = +100˚C ± 2.2 ± 4.7 ± 3.2 ˚C (max)
TA = +85˚C ± 2.1 ± 4.6 ± 3.1 ˚C (max)
TA = +80˚C ± 2.0 ± 4.5 ± 3.0 ˚C (max)
TA = 0˚C ± 1.9 ± 4.4 ± 2.9 ˚C (max)
TA = −30˚C ± 2.2 ± 4.7 ± 3.3 ˚C (min)
TA = −40˚C ± 2.3 ± 4.8 ± 3.5 ˚C (max)
TA = −55˚C ± 2.5 ± 5.0 ˚C (max)
Output Voltage at 0˚C +1.8639 V
Variance from Curve ± 1.0 ˚C
Non-Linearity (Note 9) −20˚C ≤ TA ≤ +80˚C ± 0.4 %
Sensor Gain (Temperature −30˚C ≤ TA ≤ +100˚C −11.77 −11.4 −11.0 −11.0 mV/˚C (min)
Sensitivity or Average Slope) −12.2 −12.6 −12.6 mV/˚C (max)
to equation:
VO = −11.77 mV/˚CxT+1.860V
Output Impedance 0 µA ≤ IL ≤ +16 µA(Notes 160 160 160 Ω (max)
11, 12)
Load Regulation(Note 10) 0 µA ≤ IL ≤ +16 µA(Notes −2.5 −2.5 −2.5 mV (max)
11, 12)
Line Regulation +2. 4 V ≤ V+ ≤ +5.0V +3.3 +3.7 +3.7 mV/V (max)
+5.0 V ≤ V+ ≤ +5.5 V +8.8 +8.9 +8.9 mV (max)
Quiescent Current +2. 4 V ≤ V+ ≤ +5.5V 4.5 7 7 7 µA (max)
+2. 4 V ≤ V+ ≤ +5.0V 4.5 10 10 10 µA (max)
Change of Quiescent Current +2. 4 V ≤ V+ ≤ +5.5V +0.7 µA
Temperature Coefficient of −11 nA/˚C
Quiescent Current
Shutdown Current V+ ≤ +0.8 V 0.02 µA

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LM20
Electrical Characteristics (Continued)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func-
tional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed speci-
fications 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 (VI) at any pin exceeds power supplies (VI < GND or VI > V+), the current at that pin should be limited to 5 mA.
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 di-
rectly into each pin.
Note 4: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in any post 1986 National Semi-
conductor Linear Data Book for other methods of soldering surface mount devices.
Note 5: The junction to ambient thermal resistance (θJA) is specified without a heat sink in still air using the printed circuit board layout shown in Figure *NO TARGET
FOR fig NS1382*.
Note 6: Typicals are at TJ = TA = 25˚C and represent most likely parametric norm.
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 (ex-
pressed 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 com-
puted 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.

Typical Performance Characteristics

Temperature Error vs Temperature

DS100908-25

PCB Layouts Used for Thermal

Measurements

DS100908-29 DS100908-30

a) Layout used for no heat sink measurements. b) Layout used for measurements with small heat hink.
FIGURE 1. PCB Lyouts used for thermal measurements.

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 LM20
1.0 LM20 Transfer Function where T is the middle of the temperature range of interest
and m is in V/˚C. For example for the temperature range of
The LM20’s transfer function can be described in different Tmin = −30 to Tmax = +100˚C:
ways with varying levels of precision. A simple linear transfer
T = 35˚C
function, with good accuracy near 25˚C, is
and
VO = −11.69 mV/˚C x T + 1.8663 V
m = −11.77 mV/˚C
Over the full operating temperature range of −55˚C to
+130˚C, best accuracy can be obtained by using the para- The offset of the linear transfer function can be calculated
bolic transfer function using the following equation:
VO = (−3.88x10−6xT2) + (−1.15x10−2xT) + 1.8639 b = (VOP(Tmax) + VOP(T) + m x (Tmax+T))/2,
solving for T: where:
• VOP(Tmax) is the calculated output voltage at Tmax using
the parabolic transfer function for VO
• VOP(T) is the calculated output voltage at T using the
parabolic transfer function for VO.
A linear transfer function can be used over a limited tempera- Using this procedure the best fit linear transfer function for
ture range by calculating a slope and offset that give best re- many popular temperature ranges was calculated in Figure
sults over that range. A linear transfer function can be calcu- 2. As shown in Figure 2 the error that is introduced by the lin-
lated from the parabolic transfer function of the LM20. The ear transfer function increases with wider temperature
slope of the linear transfer function can be calculated using ranges.
the following equation:
m = −7.76 x 10−6x T − 0.0115,

Temperature Range Linear Equation Maximum Deviation of Linear

VO = Equation from Parabolic Equation
Tmin (˚C) Tmax (˚C)
(˚C)
−55 +130 −11.79 mV/˚C x T + 1.8528 V ± 1.41
−40 +110 −11.77 mV/˚C x T + 1.8577 V ± 0.93
−30 +100 −11.77 mV/˚C x T + 1.8605 V ± 0.70
-40 +85 −11.67 mV/˚C x T + 1.8583 V ± 0.65
−10 +65 −11.71 mV/˚C x T + 1.8641 V ± 0.23
+35 +45 −11.81 mV/˚C x T + 1.8701 V ± 0.004
+20 +30 −11.69 mV/˚C x T + 1.8663 V ± 0.004
FIGURE 2. First order equations optimized for different temperature ranges.

2.0 Mounting as Humiseal and epoxy paints or dips are often used to en-
sure that moisture cannot corrode the LM20 or its connec-
The LM20 can be applied easily in the same way as other tions.
integrated-circuit temperature sensors. It can be glued or ce-
The thermal resistance junction to ambient (θJA) is the pa-
mented to a surface. The temperature that the LM20 is sens-
rameter used to calculate the rise of a device junction tem-
ing will be within about +0.02˚C of the surface temperature to
perature due to its power dissipation. For the LM20 the
which the LM20’s leads are attached to.
equation used to calculate the rise in the die temperature is
This presumes that the ambient air temperature is almost the as follows:
same as the surface temperature; if the air temperature were
TJ = TA + θJA [(V+ IQ) + (V+ − VO) IL]
much higher or lower than the surface temperature, the ac-
tual temperature measured would be at an intermediate tem- where IQ is the quiescent current and ILis the load current on
perature between the surface temperature and the air tem- the output. Since the LM20’s junction temperature is the ac-
perature. tual temperature being measured care should be taken to
minimize the load current that the LM20 is required to drive.
To ensure good thermal conductivity the backside of the
LM20 die is directly attached to the pin 2 GND pin. The tem- The tables shown in Figure 3 summarize the rise in die tem-
pertures of the lands and traces to the other leads of the perature of the LM20 without any loading, and the thermal
LM20 will also affect the temperature that is being sensed. resistance for different conditions.
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 conden-
sation can occur. Printed-circuit coatings and varnishes such

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LM20
2.0 Mounting (Continued) 3.0 Capacitive Loads
The LM20 handles capacitive loading well. Without any pre-
cautions, the LM20 can drive any capacitive load less than
SC70-5 SC70-5 300 pF as shown in Figure 4. Over the specified temperature
no heat sink small heat sink range the LM20 has a maximum output impedance of 160 Ω.
In an extremely noisy environment it may be necessary to
θJA TJ − TA θJA TJ − TA
add some filtering to minimize noise pickup. It is recom-
(˚C/W) (˚C) (˚C/W) (˚C) mended that 0.1 µF be added from V+ to GND to bypass the
Still air 412 0.2 350 0.19 power supply voltage, as shown in Figure 5. In a noisy envi-
Moving 312 0.17 266 0.15 ronment it may even be necessary to add a capacitor from
the output to ground with a series resistor as shown in Figure
air
5. A 1 µF output capacitor with the 160 Ω maximum output
See Figure 1 for PCB layout samples. impedance and a 200 Ω series resistor will form a 442 Hz
lowpass filter. Since the thermal time constant of the LM20 is
micro SMD micro SMD much slower, the overall response time of the LM20 will not
be significantly affected.
no heat sink small heat fin
θJA TJ − TA θJA TJ − TA
(˚C/W) (˚C) (˚C/W) (˚C)
Still air TBD TBD TBD TBD
Moving TBD TBD TBD TBD
air DS100908-15

FIGURE 4. LM20 No Decoupling Required for

FIGURE 3. Temperature Rise of LM20 Due to Capacitive Loads Less than 300 pF.
Self-Heating and Thermal Resistance (θJA)

R (Ω) C (µF)
200 1
470 0.1
680 0.01
1k 0.001

DS100908-16

DS100908-33

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 placed inside an enclosure of some type that minimizes its
may cause the output reading of the LM20 to drop by 1.5V. In light exposure. Most chassis provide more than ample pro-
a normal office environment of fluorescent lighting the output tection. The LM20 does not sustain permanent damage from
voltage is minimally affected (less than a millivolt drop). In ei- light exposure. Removing the light source will cause LM20’s
ther case it is recommended that the LM20 micro SMD be output voltage to recover to the proper value.

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 LM20
5.0 Applications Circuits

DS100908-18

FIGURE 6. Centigrade Thermostat

DS100908-19

FIGURE 7. Conserving Power Dissipation with Shutdown

DS100908-28

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

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LM20
Physical Dimensions inches (millimeters) unless otherwise noted

5-Lead SC70 Molded Package

Order Number LM20BIM7 or LM20CIM7X
NS Package Number MAA05A

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 LM20 2.4V, 10µA, SC70, micro SMD Temperature Sensor
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

4-Bump micro SMD Ball Grid Array Package

Order Number LM20SIBP or LM20SIBPX
NS Package Number BPA04DDC
The following dimensions apply to the BPA04DDC package
shown above: X1=X2 = 853µm ± 30µm, X3= 900µm ± 50µm

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labeling, can be reasonably expected to result in a
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