LM61
February 9, 2010
2.7V, SOT-23 or TO-92 Temperature Sensor
General Description
The LM61 is a precision integrated-circuit temperature sensor
that can sense a −30°C to +100°C temperature range while
operating from a single +2.7V supply. The LM61's output volt-
age is linearly proportional to Celsius (Centigrade) tempera-
ture (+10 mV/°C) and has a DC offset of +600 mV. The offset
allows reading negative temperatures without the need for a
negative supply. The nominal output voltage of the LM61
ranges from +300 mV to +1600 mV for a −30°C to +100°C
temperature range. The LM61 is calibrated to provide accu-
racies of ±2.0°C at room temperature and ±3°C over the full
−25°C to +85°C temperature range.
The LM61's linear output, +600 mV offset, and factory cali-
bration simplify external circuitry required in a single supply
environment where reading negative temperatures is re-
quired. Because the LM61's quiescent current is less than
125 μA, self-heating is limited to a very low 0.2°C in still air.
Shutdown capability for the LM61 is intrinsic because its in-
herent low power consumption allows it to be powered directly
from the output of many logic gates.
Features
■Calibrated linear scale factor of +10 mV/°C
■Rated for full −30° to +100°C range
■Suitable for remote applications
■UL Recognized Component
Applications
■Cellular Phones
■Computers
■Power Supply Modules
■Battery Management
■FAX Machines
■Printers
■HVAC
■Disk Drives
■Appliances
Key Specifications
■ Accuracy at 25°C ±2.0 or ±3.0°C
(max)
■ Accuracy for −30°C to +100°C ±4.0°C (max)
■ Accuracy for −25°C to +85°C ±3.0°C (max)
■ Temperature Slope +10 mV/°C
■ Power Supply Voltage Range +2.7V to +10V
■ Current Drain @ 25°C 125 µA (max)
■ Nonlinearity ±0.8°C (max)
■ Output Impedance 800 Ω (max)
Typical Application
1289702
VO = (+10 mV/°C × T °C) + 600 mV
Temperature (T) Typical VO
+100°C +1600 mV
+85°C +1450 mV
+25°C +850 mV
0°C +600 mV
−25°C +350 mV
−30°C +300 mV
FIGURE 1. Full-Range Centigrade Temperature Sensor (−30°C to +100°C)
Operating from a Single Li-Ion Battery Cell
© 2010 National Semiconductor Corporation 12897 www.national.com
LM61 2.7V, SOT-23 or TO-92 Temperature Sensor
Connection Diagrams
SOT-23
1289701
Top View
See NS Package Number mf03a
TO-92
1289725
See NS Package Number Z03A
Ordering Information
Order
Number
Device
Top Mark Supplied In
Accuracy
Over
Specified
Temperature
Range (°C)
Specified
Temperature
Range
Package
Type
LM61BIM3 T1B 1000 Units on Tape and Reel ± 3 −25°C to +85°C
SOT-23
LM61BIM3X T1B 3000 Units on Tape and Reel
LM61CIM3 T1C 1000 Units on Tape and Reel ± 4 −30°C to +100°C
LM61CIM3X T1C 3000 Units on Tape and Reel
LM61BIZ LM61BIZ Bulk ± 3 −25°C to +85°C TO-92
LM61CIZ LM61CIZ Bulk ± 4 −30°C to +100°C
www.national.com 2
LM61
Absolute Maximum Ratings (Note 1)
Supply Voltage +12V to −0.2V
Output Voltage (+VS + 0.6V) to
−0.6V
Output Current 10 mA
Input Current at any pin (Note 2) 5 mA
Storage Temperature −65°C to +150°C
Maximum Junction Temperature
(TJMAX)+125°C
ESD Susceptibility (Note 3) :
Human Body Model 2500V
Machine Model 250V
Operating Ratings (Note 1)
Specified Temperature Range: TMIN ≤ TA ≤ TMAX
LM61C −30°C ≤ TA ≤ +100°C
LM61B −25°C ≤ TA ≤ +85°C
Supply Voltage Range (+VS)+2.7V to +10V
Thermal Resistance, θJA(Note 5)
SOT-23
TO-92
450°C/W
180°C/W
Soldering process must comply with National
Semiconductor's Reflow Temperature Profile specifications.
Refer to www.national.com/packaging. (Note 4)
Electrical Characteristics
Unless otherwise noted, these specifications apply for +VS = +3.0 VDC. Boldface limits apply for TA = TJ = TMIN to TMAX ; all other
limits TA = TJ = 25°C.
Parameter Conditions Typical
(Note 6)
LM61B LM61C Units
(Limit)
Limits Limits
(Note 7) (Note 7)
Accuracy (Note 8) ±2.0 ±3.0 °C (max)
±3.0 ±4.0 °C (max)
Output Voltage at 0°C +600 mV
Nonlinearity (Note 9) ±0.6 ±0.8 °C (max)
Sensor Gain +10 +9.7 +9.6 mV/°C (min)
(Average Slope) +10.3 +10.4 mV/°C (max)
Output Impedance +3.0V ≤ +VS ≤ +10V
−30°C ≤ TA ≤ +85°C, +VS= +2.7V
+85°C ≤ TA ≤ +100°C, +VS= +2.7V
0.8
2.3
5
0.8
2.3
5
kΩ (max)
kΩ (max)
kΩ (max)
Line Regulation (Note 10)+3.0V ≤ +VS ≤ +10V ±0.7 ±0.7 mV/V (max)
+2.7V ≤ +VS ≤ +3.3V ±5.7 ±5.7 mV (max)
Quiescent Current +2.7V ≤ +VS ≤ +10V 82 125 125 µA (max)
155 155 µA (max)
Change of Quiescent Current +2.7V ≤ +VS ≤ +10V ±5 μA
Temperature Coefficient of 0.2 µA/°C
Quiescent Current
Long Term Stability (Note 11) TJ=TMAX=+100°C,
for 1000 hours ±0.2 °C
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 > +VS), 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.
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 output voltage and +10 mV/°C times the device's case temperature plus 600 mV, at specified conditions of
voltage, current, and temperature (expressed in °C).
Note 9: 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 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.
3 www.national.com
LM61
Note 11: 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.
The majority of the drift will occur in the first 1000 hours at elevated temperatures. The drift after 1000 hours will not continue at the first 1000 hour rate.
Typical Performance Characteristics The LM61 in the SOT-23 package mounted to a printed circuit
board as shown in Figure 2 was used to generate the following thermal curves.
Thermal Resistance
Junction to Air
1289703
Thermal Time Constant
1289704
Thermal Response in
Still Air with Heat Sink
1289705
Thermal Response
in Stirred Oil Bath
with Heat Sink
1289706
Thermal Response in Still
Air without a Heat Sink
1289708
Quiescent Current
vs. Temperature
1289709
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LM61
Accuracy vs Temperature
1289710
Noise Voltage
1289711
Supply Voltage
vs Supply Current
1289712
Start-Up Response
1289722
1289714
FIGURE 2. Printed Circuit Board Used
for Heat Sink to Generate All Curves.
½″ Square Printed Circuit Board
with 2 oz. Copper Foil or Similar.
5 www.national.com
LM61
1.0 Mounting
The LM61 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or ce-
mented to a surface. The temperature that the LM61 is sens-
ing will be within about +0.2°C of the surface temperature that
LM61'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 temper-
ature between the surface temperature and the air tempera-
ture.
To ensure good thermal conductivity the backside of the
LM61 die is directly attached to the GND pin. The lands and
traces to the LM61 will, of course, be part of the printed circuit
board, which is the object whose temperature is being mea-
sured.
Alternatively, the LM61 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 LM61 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 LM61 or its connections.
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 LM61 the
equation used to calculate the rise in the die temperature is
as follows:
TJ = TA + θJA [(+VS IQ) + (+VS − VO) IL]
where IQ is the quiescent current and ILis the load current on
the output. Since the LM61's junction temperature is the ac-
tual temperature being measured care should be taken to
minimize the load current that the LM61 is required to drive.
The table shown in Figure 3 summarizes the rise in die tem-
perature of the LM61 without any loading with a 3.3V supply,
and the thermal resistance for different conditions.
SOT-23* SOT-23** TO-92* TO-92***
no heat sink small heat fin no heat sink small heat fin
θJA TJ − TAθJA TJ − TAθJA TJ − TAθJA TJ − TA
(°C/W) (°C) (°C/W) (°C) (°C/W) (°C) (°C/W) (°C)
Still air 450 0.26 260 0.13 180 0.09 140 0.07
Moving air 180 0.09 90 0.05 70 0.03
*Part soldered to 30 gauge wire.
**Heat sink used is ½″ square printed circuit board with 2 oz. foil with part attached as shown in Figure 2.
***Part glued and leads soldered to 1" square of 1/16" printed circuit board with 2oz. foil or similar.
FIGURE 3. Temperature Rise of LM61 Due to
Self-Heating and Thermal Resistance (θJA)
2.0 Capacitive Loads
The LM61 handles capacitive loading well. Without any spe-
cial precautions, the LM61 can drive any capacitive load as
shown in Figure 4. Over the specified temperature range the
LM61 has a maximum output impedance of 5 kΩ. In an ex-
tremely noisy environment it may be necessary to add some
filtering to minimize noise pickup. It is recommended that
0.1 μF be added from +VS to GND to bypass the power supply
voltage, as shown in Figure 5. In a noisy environment it may
be necessary to add a capacitor from the output to ground. A
1 μF output capacitor with the 5 kΩ maximum output
impedance will form a 32 Hz lowpass filter. Since the thermal
time constant of the LM61 is much slower than the 5 ms time
constant formed by the RC, the overall response time of the
LM61 will not be significantly affected. For much larger ca-
pacitors this additional time lag will increase the overall re-
sponse time of the LM61.
1289715
FIGURE 4. LM61 No Decoupling Required for Capacitive
Load
1289716
FIGURE 5. LM61 with Filter for Noisy Environment
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LM61
1289717
FIGURE 6. Simplified Schematic
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LM61
3.0 Applications Circuits
1289718
FIGURE 7. Centigrade Thermostat
1289719
FIGURE 8. Conserving Power Dissipation with Shutdown
4.0 Recommended Solder Pads for SOT-23 Package
1289720
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LM61
Physical Dimensions inches (millimeters) unless otherwise noted
SOT-23 Molded Small Outline Transistor Package (M3)
Order Number LM61BIM3, LM61BIM3X, LM61CIM3 or LM61CIM3X
NS Package Number mf03a
9 www.national.com
LM61
TO-92 Plastic Package (Z)
Order Number LM61BIZ or LM61CIZ
NS Package Number Z03A
www.national.com 10
LM61
Notes
11 www.national.com
LM61
Notes
LM61 2.7V, SOT-23 or TO-92 Temperature Sensor
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