National Semiconductor is now part of
Texas Instruments.
Search http://www.ti.com/ for the latest technical
information and details on our current products and services.
LM20
2.4V, 10µA, SC70, micro SMD Temperature Sensor
General Description
The LM20 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 LM20 is predominately linear, yet has a slight predictable parabolic curvature.
The accuracy of the LM20 when specified to a parabolic
transfer function is ±1.5°C at an ambient temperature of +30°
C. The temperature error increases linearly and reaches a
maximum of ±2.5°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 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.
Applications
■
■
■
■
Cellular Phones
Computers
Power Supply Modules
Battery Management
■
■
■
■
■
FAX Machines
Printers
HVAC
Disk Drives
Appliances
Features
■
■
■
■
Rated for full −55°C to +130°C range
Available in an SC70 and micro SMD package
Predictable curvature error
Suitable for remote applications
Key Specifications
■ Accuracy at +30°C
■ Accuracy at +130°C & −55°C
■ Power Supply Voltage Range
■ Current Drain
■ Nonlinearity
■ Output Impedance
■ Load Regulation
0 μA < IL< +16 μA
±1.5 to ±4 °C (max)
±2.5 to ±5 °C (max)
+2.4V to +5.5V
10 μA (max)
±0.4 % (typ)
160 Ω (max)
−2.5 mV (max)
Typical Application
Full-Range Celsius (Centigrade) Temperature Sensor (−55°C to +130°C)
Operating from a Single Li-Ion Battery Cell
Output Voltage vs Temperature
10090802
VO = (−3.88×10−6×T2) + (−1.15×10−2×T) + 1.8639
where:
T is temperature, and VO is the measured output voltage of the LM20.
© 2011 National Semiconductor Corporation
100908
10090824
www.national.com
LM20 2.4V, 10µA, SC70, micro SMD Temperature Sensor
September 21, 2010
LM20
Temperature (T)
Typical VO
+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
Connection Diagrams
SC70-5
micro SMD
10090801
Note:
10090832
- GND (pin 2) may be grounded or left floating. For optimum thermal conNote:
ductivity to the pc board ground plane pin 2 should be grounded.
- NC (pin 1) should be left floating or grounded. Other signal traces should - Pin numbers are referenced to the package marking text orientation.
- Reference JEDEC Registration MO-211, variation BA
not be connected to this pin.
- The actual physical placement of package marking will vary slightly from
Top View
part to part. The package marking will designate the date code and will vary conSee NS Package Number MAA05A
siderably. Package marking does not correlate to device type in any way.
Top View
See NS Package Number TLA04ZZA
Ordering Information
Order
Number
Temperature
Accuracy
Temperature
Range
NS Package
Number
Device
Marking
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
LM20SITL
±3.5°C
−40°C to +125°C
TLA04ZZA
Date Code 250 Units on Tape and Reel
LM20SITLX
±3.5°C
−40°C to +125°C
TLA04ZZA
Date Code 3000 Units on Tape and Reel
www.national.com
2
Transport Media
Supply Voltage
Output Voltage
Output Current
Input Current at any pin (Note 2)
Storage Temperature
(Note 1)
Specified Temperature Range:
+6.5V to −0.2V
(V+ + 0.6 V) to
−0.6 V
10 mA
5 mA
−65°C to
+150°C
+150°C
LM20B, LM20C with
2.4 V ≤ V+≤ 2.7 V
LM20B, LM20C with
2.7 V ≤ V+≤ 5.5 V
LM20S with
2.4 V ≤ V+≤ 5.5 V
LM20S with
2.7 V ≤ V+≤ 5.5 V
Supply Voltage Range (V+)
Maximum Junction Temperature (TJMAX)
ESD Susceptibility (Note 3)
Human Body Model
2500 V
Machine Model
250 V
Soldering process must comply with National's
Reflow Temperature Profile specifications. Refer to
www.national.com/packaging. (Note 4)
LM20
Operating Ratings
Absolute Maximum Ratings (Note 1)
TMIN ≤ TA ≤ TMAX
−30°C ≤ TA ≤ +130°C
−55°C ≤ TA ≤ +130°C
−30°C ≤ TA ≤ +125°C
−40°C ≤ TA ≤ +125°C
+2.4 V to +5.5 V
Thermal Resistance, θJA (Note 5)
SC-70
micro SMD
415°C/W
340°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.
LM20B
LM20C
LM20S
Limits
(Note 7)
Limits
(Note 7)
Limits
(Note 7)
TA = +25°C to +30°C
±1.5
±4.0
±2.5
TA = +130°C
±2.5
±5.0
TA = +125°C
±2.5
±5.0
±3.5
°C (max)
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)
±2.5
±5.0
Parameter
Temperature to Voltage Error
VO = (−3.88×10−6×T2)
+ (−1.15×10−2×T) + 1.8639V
(Note 8)
Typical
(Note 6)
Conditions
TA = −55°C
Output Voltage at 0°C
Variance from Curve
Non-Linearity (Note 9)
−20°C ≤ TA ≤ +80°C
Sensor Gain (Temperature
Sensitivity or Average Slope) to
−30°C ≤ TA ≤ +100°C
equation:
VO=−11.77 mV/°C×T+1.860V
Output Impedance
0 μA ≤ IL ≤ +16 μA
Load Regulation(Note 10)
0 μA ≤ IL ≤ +16 μA
Line Regulation
Quiescent Current
Change of Quiescent Current
Units
(Limit)
°C (max)
°C (max)
°C (max)
+1.8639
V
±1.0
°C
±0.4
%
−11.77
−11.4
−12.2
−11.0
−12.6
−11.0
−12.6
mV/°C (min)
mV/°C (max)
160
160
160
Ω (max)
−2.5
−2.5
−2.5
mV (max)
+3.3
+3.7
+3.7
mV/V (max)
(Note 11, Note 12)
(Note 11, Note 12)
+2. 4 V ≤ V+ ≤ +5.0V
+5.0 V ≤ V+ ≤ +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)
+2. 4 V ≤ V+ ≤ +5.5V
+0.7
+2. 4V ≤
V+
+5.0V ≤
V+
+2. 4V ≤
V+
3
μA
www.national.com
LM20
Parameter
Typical
(Note 6)
Conditions
Temperature Coefficient of
Quiescent Current
Shutdown Current
V+ ≤ +0.8 V
LM20B
LM20C
LM20S
Limits
(Note 7)
Limits
(Note 7)
Limits
(Note 7)
Units
(Limit)
−11
nA/°C
0.02
μA
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 (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
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 (θJA) is specified without a heat sink in still air using the printed circuit board layout shown in Figure 1.
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
(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.
Typical Performance Characteristics
Temperature Error vs Temperature
10090825
www.national.com
4
LM20
PCB Layouts Used for Thermal Measurements
10090830
10090829
b) Layout used for measurements with small heat hink.
a) Layout used for no heat sink measurements.
FIGURE 1. PCB Lyouts used for thermal measurements.
m = −7.76 × 10−6× T − 0.0115,
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 TMIN
= −30 to TMAX = +100°C:
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
T = 35°C
VO = −11.69 mV/°C × T + 1.8663 V
and
Over the full operating temperature range of −55°C to +130°
C, best accuracy can be obtained by using the parabolic
transfer function.
m = −11.77 mV/°C
The offset of the linear transfer function can be calculated using the following equation:
VO = (−3.88×10−6×T2) + (−1.15×10−2×T) + 1.8639
b = (VOP(TMAX) + VOP(T) − m × (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.
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.
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:
Temperature Range
Linear Equation
VO =
Maximum Deviation of Linear Equation from
Parabolic Equation (°C)
Tmin (°C)
Tmax (°C)
−55
+130
−11.79 mV/°C × T + 1.8528 V
±1.41
−40
+110
−11.77 mV/°C × T + 1.8577 V
±0.93
−30
+100
−11.77 mV/°C × T + 1.8605 V
±0.70
-40
+85
−11.67 mV/°C × T + 1.8583 V
±0.65
−10
+65
−11.71 mV/°C × T + 1.8641 V
±0.23
+35
+45
−11.81 mV/°C × T + 1.8701 V
±0.004
+20
+30
−11.69 mV/°C × T + 1.8663 V
±0.004
FIGURE 2. First order equations optimized for different temperature ranges.
5
www.national.com
LM20
2.0 Mounting
3.0 Capacitive Loads
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 (θJA) is the parameter used to calculate the rise of a device junction temperature due to its power dissipation. For the LM20 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 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.
The LM20 handles capacitive loading well. Without any precautions, the LM20 can drive any capacitive load less than
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 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.
SC70-5
no heat sink
10090815
FIGURE 4. LM20 No Decoupling Required for Capacitive
Loads Less than 300 pF.
R (Ω)
C (µF)
200
1
470
0.1
680
0.01
1k
0.001
SC70-5
small heat sink
θJA
TJ − TA
θJA
TJ − TA
(°C/W)
(°C)
(°C/W)
(°C)
Still air
412
0.2
350
0.19
Moving air
312
0.17
266
0.15
10090816
See Figure 1 for PCB layout samples.
micro SMD
no heat sink
θJA
micro SMD
small heat fin
TJ − TA
θJA
TJ − TA
(°C/W)
(°C)
(°C/W)
(°C)
Still air
340
0.18
TBD
TBD
Moving air
TBD
TBD
TBD
TBD
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.
FIGURE 3. Temperature Rise of LM20 Due to
Self-Heating and Thermal Resistance (θJA)
www.national.com
6
LM20
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 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
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
7
www.national.com
LM20
Physical Dimensions inches (millimeters) unless otherwise noted
5-Lead SC70 Molded Package
Order Number LM20BIM7 or LM20CIM7X
NS Package Number MAA05A
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
www.national.com
8
LM20
Notes
9
www.national.com
LM20 2.4V, 10µA, SC70, micro SMD Temperature Sensor
Notes
For more National Semiconductor product information and proven design tools, visit the following Web sites at:
www.national.com
Products
Design Support
Amplifiers
www.national.com/amplifiers
WEBENCH® Tools
www.national.com/webench
Audio
www.national.com/audio
App Notes
www.national.com/appnotes
Clock and Timing
www.national.com/timing
Reference Designs
www.national.com/refdesigns
Data Converters
www.national.com/adc
Samples
www.national.com/samples
Interface
www.national.com/interface
Eval Boards
www.national.com/evalboards
LVDS
www.national.com/lvds
Packaging
www.national.com/packaging
Power Management
www.national.com/power
Green Compliance
www.national.com/quality/green
Switching Regulators
www.national.com/switchers
Distributors
www.national.com/contacts
LDOs
www.national.com/ldo
Quality and Reliability
www.national.com/quality
LED Lighting
www.national.com/led
Feedback/Support
www.national.com/feedback
Voltage References
www.national.com/vref
Design Made Easy
www.national.com/easy
www.national.com/powerwise
Applications & Markets
www.national.com/solutions
Mil/Aero
www.national.com/milaero
PowerWise® Solutions
Serial Digital Interface (SDI) www.national.com/sdi
Temperature Sensors
www.national.com/tempsensors SolarMagic™
www.national.com/solarmagic
PLL/VCO
www.national.com/wireless
www.national.com/training
PowerWise® Design
University
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2011 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Technical
Support Center
Email: support@nsc.com
Tel: 1-800-272-9959
www.national.com
National Semiconductor Europe
Technical Support Center
Email: europe.support@nsc.com
National Semiconductor Asia
Pacific Technical Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Technical Support Center
Email: jpn.feedback@nsc.com