LM45
SOT-23 Precision Centigrade Temperature Sensors
General Description
The LM45 series are precision integrated-circuit temperature
sensors, whose output voltage is linearly proportional to the
Celsius (Centigrade) temperature. The LM45 does not re-
quire any external calibration or trimming to provide accura-
cies of ±2˚C at room temperature and ±3˚C over a full −20 to
+100˚C temperature range. Low cost is assured by trimming
and calibration at the wafer level. The LM45’s low output im-
pedance, linear output, and precise inherent calibration
make interfacing to readout or control circuitry especially
easy. It can be used with a single power supply, or with plus
and minus supplies. As it draws only 120 µA from its supply,
it has very low self-heating, less than 0.2˚C in still air. The
LM45 is rated to operate over a −20˚ to +100˚C temperature
range.
Applications
nBattery Management
nFAX Machines
nPrinters
nPortable Medical Instruments
nHVAC
nPower Supply Modules
nDisk Drives
nComputers
nAutomotive
Features
nCalibrated directly in ˚ Celsius (Centigrade)
nLinear + 10.0 mV/˚C scale factor
n±3˚C accuracy guaranteed
nRated for full −20˚ to +100˚C range
nSuitable for remote applications
nLow cost due to wafer-level trimming
nOperates from 4.0V to 10V
nLess than 120 µA current drain
nLow self-heating, 0.20˚C in still air
nNonlinearity only ±0.8˚C max over temp
nLow impedance output, 20Ωfor 1 mA load
Connection Diagram SOT-23
Order Device
Number Marking Supplied As
LM45BIM3 T4B 1000 Units on Tape and Reel
LM45BIM3X T4B 3000 Units on Tape and Reel
LM45CIM3 T4C 1000 Units on Tape and Reel
LM45CIM3X T4C 3000 Units on Tape and Reel
Typical Applications
SOT-23
DS011754-1
Top View
See NS Package Number MA03B
DS011754-3
FIGURE 1. Basic Centigrade Temperature
Sensor (+2.5˚C to +100˚C)
DS011754-4
Choose R1=−V
S
/50 µA
VOUT= (10 mV/˚C x Temp ˚C)
VOUT = +1,000 mV at +100˚C
= +250 mV at +25˚C
= −200 mV at −20˚C
FIGURE 2. Full-Range Centigrade
Temperature Sensor (−20˚C to +100˚C)
August 1999
LM45 SOT-23 Precision Centigrade Temperature Sensors
© 2000 National Semiconductor Corporation DS011754 www.national.com
Absolute Maximum Ratings (Note 1)
Supply Voltage +12V to −0.2V
Output Voltage +V
S
+ 0.6V to
−1.0V
Output Current 10 mA
Storage Temperature −65˚C to +150˚C
Lead Temperature:
SOT Package (Note 2):
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
ESD Susceptibility (Note 3):
Human Body Model
Machine Model 2000V
250V
Operating Ratings (Note 1)
Specified Temperature Range
(Note 4) T
MIN
to T
MAX
LM45B, LM45C −20˚C to +100˚C
Operating Temperature Range
LM45B, LM45C −40˚C to +125˚C
Supply Voltage Range (+V
S
) +4.0V to +10V
Electrical Characteristics
Unless otherwise noted, these specifications apply for +V
S
= +5Vdc and I
LOAD
= +50 µA, in the circuit of
Figure 2
. These
specifications also apply from +2.5˚C to T
MAX
in the circuit of
Figure 1
for +V
S
= +5Vdc. Boldface limits apply for T
A
=T
J
=
T
MIN
to T
MAX
; all other limits T
A
=T
J
= +25˚C, unless otherwise noted.
Parameter Conditions LM45B LM45C Units
(Limit)
Typical Limit Typical Limit
(Note 5) (Note 5)
Accuracy T
A
=+25˚C ±2.0 ±3.0 ˚C (max)
(Note 6) T
A
=T
MAX
±3.0 ±4.0 ˚C (max)
T
A
=T
MIN
±3.0 ±4.0 ˚C (max)
Nonlinearity T
MIN
≤T
A
≤T
MAX
±0.8 ±0.8 ˚C (max)
(Note 7)
Sensor Gain T
MIN
≤T
A
≤T
MAX
+9.7 +9.7 mV/˚C (min)
(Average Slope) +10.3 +10.3 mV/˚C (max)
Load Regulation (Note 8) 0≤I
L
≤+1 mA ±35 ±35 mV/mA
(max)
Line Regulation +4.0V≤+V
S
≤+10V ±0.80 ±0.80 mV/V (max)
(Note 8) ±1.2 ±1.2 mV/V (max)
Quiescent Current +4.0V≤+V
S
≤+10V, +25˚C 120 120 µA (max)
(Note 9) +4.0V≤+V
S
≤+10V 160 160 µA (max)
Change of Quiescent 4.0V≤+V
S
≤10V 2.0 2.0 µA (max)
Current (Note 9)
Temperature Coefficient +2.0 +2.0 µA/˚C
of Quiescent Current
Minimum Temperature In circuit of +2.5 +2.5 ˚C (min)
for Rated Accuracy
Figure 1
,I
L
=0
Long Term Stability (Note 10) T
J
=T
MAX
, for 1000 hours ±0.12 ±0.12 ˚C
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its rated operating conditions.
Note 2: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National Semicon-
ductor Linear Data Book for other methods of soldering surface mount devices.
Note 3: Human body model, 100 pF discharged through a 1.5 kΩresistor. Machine model, 200 pF discharged directly into each pin.
Note 4: Thermal resistance of the SOT-23 package is 260˚C/W, junction to ambient when attached to a printed circuit board with 2 oz. foil as shown in
Figure 3
.
Note 5: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 6: Accuracy is defined as the error between the output voltage and 10 mv/˚C times the device’s case temperature, at specified conditions of voltage, current,
and temperature (expressed in ˚C).
Note 7: Nonlinearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line, over the device’s rated temperature
range.
Note 8: 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 9: Quiescent current is measured using the circuit of
Figure 1
.
Note 10: For best long-term stability, any precision circuit will give best results if the unit is aged at a warm temperature, and/or temperature cycled for at least 46
hours before long-term life test begins. This is especially true when a small (Surface-Mount) part is wave-soldered; allow time for stress relaxation to occur.
LM45
www.national.com 2
Typical Performance Characteristics To generate these curves the LM45 was mounted to a printed
circuit board as shown in
Figure 3
.
Thermal Resistance
Junction to Air
DS011754-24
Thermal Time Constant
DS011754-25
Thermal Response in Still Air
with Heat Sink (
Figure 3
)
DS011754-26
Thermal Response
in Stirred Oil Bath
with Heat Sink
DS011754-27
Start-Up Voltage
vs Temperature
DS011754-28
Quiescent Current
vs Temperature
(In Circuit of
Figure 1
)
DS011754-29
Quiescent Current
vs Temperature
(In Circuit of
Figure 2
)
DS011754-30
Accuracy vs Temperature
(Guaranteed)
DS011754-31
Noise Voltage
DS011754-32
LM45
www.national.com3
Typical Performance Characteristics To generate these curves the LM45 was mounted to a printed
circuit board as shown in
Figure 3
. (Continued)
Applications
The LM45 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or ce-
mented to a surface and its temperature will be within about
0.2˚C of the surface temperature.
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 ac-
tual temperature of the LM45 die would be at an intermediate
temperature between the surface temperature and the air
temperature.
To ensure good thermal conductivity the backside of the
LM45 die is directly attached to the GND pin. The lands and
traces to the LM45 will, of course, be part of the printed cir-
cuit board, which is the object whose temperature is being
measured. These printed circuit board lands and traces will
not cause the LM45s temperature to deviate from the de-
sired temperature.
Alternatively, the LM45 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 LM45 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 in-
sure that moisture cannot corrode the LM45 or its connec-
tions.
Temperature Rise of LM45 Due to Self-Heating
(Thermal Resistance)
SOT-23 SOT-23
no heat sink*small heat fin**
Still air 450˚C/W 260˚C/W
Moving air 180˚C/W
*Part soldered to 30 gauge wire.
**Heat sink used is
1
⁄
2
” square printed circuit board with 2 oz. foil with part at-
tached as shown in
Figure 3
.
Supply Voltage
vs Supply Current
DS011754-33
Start-Up Response
DS011754-34
DS011754-23
FIGURE 3. Printed Circuit Board Used for Heat Sink to Generate All Curves.
1
⁄
2
" Square Printed Circuit Board with 2 oz. Foil or Similar
LM45
www.national.com 4
Typical Applications
CAPACITIVE LOADS
Like most micropower circuits, the LM45 has a limited ability
to drive heavy capacitive loads. The LM45 by itself is able to
drive 500 pF without special precautions. If heavier loads are
anticipated, it is easy to isolate or decouple the load with a
resistor; see
Figure 4
. Or you can improve the tolerance of
capacitance with a series R-C damper from output to
ground; see
Figure 5
.
Any linear circuit connected to wires in a hostile environment
can have its performance affected adversely by intense elec-
tromagnetic sources such as relays, radio transmitters, mo-
tors with arcing brushes, SCR transients, etc, as its wiring
can act as a receiving antenna and its internal junctions can
act as rectifiers. For best results in such cases, a bypass ca-
pacitor from V
IN
to ground and a series R-C damper such as
75Ωin series with 0.2 or 1 µF from output to ground, as
shown in
Figure 5
, are often useful.
DS011754-8
FIGURE 4. LM45 with Decoupling from Capacitive Load
DS011754-9
FIGURE 5. LM45 with R-C Damper
DS011754-12
FIGURE 6. Temperature Sensor,
Single Supply, −20˚C to +100˚C
DS011754-14
FIGURE 7. 4-to-20 mA Current Source (0˚C to +100˚C)
DS011754-15
FIGURE 8. Fahrenheit Thermometer
DS011754-16
FIGURE 9. Centigrade Thermometer (Analog Meter)
LM45
www.national.com5
Typical Applications (Continued)
DS011754-17
FIGURE 10. Expanded Scale Thermometer
(50˚ to 80˚ Fahrenheit, for Example Shown)
DS011754-18
FIGURE 11. Temperature To Digital Converter (Serial Output) (+128˚C Full Scale)
DS011754-19
FIGURE 12. Temperature To Digital Converter (Parallel TRI-STATE ®Outputs for
Standard Data Bus to µP Interface) (128˚C Full Scale)
LM45
www.national.com 6
Typical Applications (Continued)
DS011754-20
* =1% or 2% film resistor
-Trim RBfor VB=3.075V
-Trim RCfor VC=1.955V
-Trim RAfor VA=0.075V + 100mV/˚C x Tambient
-Example, VA=2.275V at 22˚C
FIGURE 13. Bar-Graph Temperature Display (Dot Mode)
DS011754-21
FIGURE 14. LM45 With Voltage-To-Frequency Converter And Isolated Output
(2.5˚C to +100˚C; 25 Hz to 1000 Hz)
LM45
www.national.com7
Block Diagram
DS011754-22
LM45
www.national.com 8
Physical Dimensions inches (millimeters) unless otherwise noted
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems 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.
2. A critical component is any component of 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
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
National Semiconductor
Europe Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
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Français Tel: +33 (0) 1 41 91 8790
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: ap.support@nsc.com
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
SOT-23 Molded Small Outline Transistor Package (M3)
Order Number LM45BIM3, LM45BIM3X, LM45CIM3 or LM45CIM3X
NS Package Number MA03B
LM45 SOT-23 Precision Centigrade Temperature Sensors
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.
National P/N LM45 - SOT-23 Precision Centigrade Temperature Sensor
See Microcontroller
Products
Products > Analog - Thermal Management > LM45
LM45 Product Folder
SOT-23 Precision Centigrade Temperature Sensor
See Also: LM50 - offset to remove negative supply voltage
Generic P/N 45
General
Description Features Datasheet Package
& Models Samples
& Pricing
Parametric Table Parametric Table
Operating Temperature Range -20 to +100 Deg C
Sensor Gain (Tmin to Tmax) 10 mV/Deg C
Supply Voltage Range +4V to +10V
Quiesent Current (mA) .16
Min. Accuracy -3 Deg C, -4 Deg C
Max. Accuracy +3 Deg C, +4 Deg C
Temp. Resolution Analog Output
Datasheet
Title Size in
Kbytes Date View Online Download Receive via
Email
LM45 SOT-23 Precision Centigrade Temperature Sensors 214
Kbytes
25-
Jul-
00 View Online Download Receive via
Email
LM45 SOT-23 Precision Centigrade Temperature Sensors
(JAPANESE)298
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View Online
Download
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If you have trouble printing or viewing PDF file(s), see Printing Problems.
Package Availability, Models, Samples & Pricing
Part Number Package Status Models Samples &
Electronic
Orders
Budgetary Pricing Std
Pack
Size
Package
Marking
Type Pins MSL SPICE IBIS Qty $US each
LM45BIM3 SOT-23 3MSL Full production N/A N/A
Samples
Buy Now
1K+ $0.5800 reel
of
1000
T4B
¢1¢T
LM45CIM3 SOT-23 3MSL Full production N/A N/A
Samples
Buy Now
1K+ $0.3000 reel
of
1000
T4C
¢1¢T
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National P/N LM45 - SOT-23 Precision Centigrade Temperature Sensor
LM45BIM3X SOT-23 3MSL Full production N/A N/A
Buy Now
1K+ $0.5800 reel
of
3000
T4B
¢1¢T
LM45B MDA Die Full production N/A N/A
Samples
tray
of
N/A -
LM45BI MDA Die Full production N/A N/A
Samples
tray
of
N/A -
LM45C MDA Die Full production N/A N/A
Samples
tray
of
N/A -
LM45CI MDA Die Full production N/A N/A
Samples
tray
of
N/A -
LM45B MWA Wafer Full production N/A N/A N/A -
LM45BI MWA Wafer Full production N/A N/A N/A -
LM45C MWA Wafer Full production N/A N/A wafer jar
of
N/A -
LM45CI MWA Wafer Full production N/A N/A N/A -
General Description
The LM45 series are precision integrated-circuit temperature sensors, whose output voltage is linearly
proportional to the Celsius (Centigrade) temperature. The LM45 does not require any external calibration or
trimming to provide accuracies of ±2°C at room temperature and ±3°C over a full -20 to +100°C
temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM45's low
output impedance, linear output, and precise inherent calibration make interfacing to readout or control
circuitry especially easy. It can be used with a single power supply, or with plus and minus supplies. As it
draws only 120 µA from its supply, it has very low self-heating, less than 0.2°C in still air. The LM45 is rated
to operate over a -20° to +100°C temperature range.
Features
● Calibrated directly in ° Celsius (Centigrade)
● Linear + 10.0 mV/°C scale factor
● ±3°C accuracy guaranteed
● Rated for full -20° to +100°C range
● Suitable for remote applications
● Low cost due to wafer-level trimming
● Operates from 4.0V to 10V
● Less than 120 µA current drain
● Low self-heating, 0.20°C in still air
● Nonlinearity only ±0.8°C max over temp
● Low impedance output, 20Ohm for 1 mA load
Applications
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National P/N LM45 - SOT-23 Precision Centigrade Temperature Sensor
● Battery Management
● FAX Machines
● Printers
● Portable Medical Instruments
● HVAC
● Power Supply Modules
● Disk Drives
● Computers
● Automotive
[Information as of 5-Aug-2002]
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