LM34
Precision Fahrenheit Temperature Sensors
General Description
The LM34 series are precision integrated-circuit temperature
sensors, whose output voltage is linearly proportional to the
Fahrenheit temperature. The LM34 thus has an advantage
over linear temperature sensors calibrated in degrees
Kelvin, as the user is not required to subtract a large con-
stant voltage from its output to obtain convenient Fahrenheit
scaling. The LM34 does not require any external calibration
or trimming to provide typical accuracies of ±
1
⁄
2
˚F at room
temperature and ±1
1
⁄
2
˚F over a full −50 to +300˚F tempera-
ture range. Low cost is assured by trimming and calibration
at the wafer level. The LM34’s low output impedance, linear
output, and precise inherent calibration make interfacing to
readout or control circuitry especially easy. It can be used
with single power supplies or with plus and minus supplies.
As it draws only 75 µA from its supply, it has very low
self-heating, less than 0.2˚F in still air. The LM34 is rated to
operate over a −50˚ to +300˚F temperature range, while the
LM34C is rated for a −40˚ to +230˚F range (0˚F with im-
proved accuracy). The LM34 series is available packaged in
hermetic TO-46 transistor packages, while the LM34C,
LM34CA and LM34D are also available in the plastic TO-92
transistor package. The LM34D is also available in an 8-lead
surface mount small outline package. The LM34 is a comple-
ment to the LM35 (Centigrade) temperature sensor.
Features
nCalibrated directly in degrees Fahrenheit
nLinear +10.0 mV/˚F scale factor
n1.0˚F accuracy guaranteed (at +77˚F)
nRated for full −50˚ to +300˚F range
nSuitable for remote applications
nLow cost due to wafer-level trimming
nOperates from 5 to 30 volts
nLess than 90 µA current drain
nLow self-heating, 0.18˚F in still air
nNonlinearity only ±0.5˚F typical
nLow-impedance output, 0.4Ωfor 1 mA load
Connection Diagrams
Note 1: Case is connected to negative pin (GND).
TO-46
Metal Can Package
(Note 1)
DS006685-1
Order Numbers LM34H,
LM34AH, LM34CH,
LM34CAH or LM34DH
See NS Package
Number H03H
TO-92
Plastic Package
DS006685-2
Order Number LM34CZ,
LM34CAZ or LM34DZ
See NS Package
Number Z03A
SO-8
Small Outline
Molded Package
DS006685-20
N.C. = No Connection
Top View
Order Number LM34DM
See NS Package Number M08A
November 2000
LM34 Precision Fahrenheit Temperature Sensors
© 2000 National Semiconductor Corporation DS006685 www.national.com
Typical Applications
DS006685-3
FIGURE 1. Basic Fahrenheit Temperature Sensor
(+5˚ to +300˚F)
DS006685-4
FIGURE 2. Full-Range Fahrenheit Temperature Sensor
LM34
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Absolute Maximum Ratings (Note 11)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage +35V to −0.2V
Output Voltage +6V to −1.0V
Output Current 10 mA
Storage Temperature,
TO-46 Package −76˚F to +356˚F
TO-92 Package −76˚F to +300˚F
SO-8 Package −65˚C to +150˚C
ESD Susceptibility (Note 12) 800V
Lead Temp.
TO-46 Package
(Soldering, 10 seconds) +300˚C
TO-92 Package
(Soldering, 10 seconds) +260˚C
SO Package (Note 13)
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
Specified Operating Temp. Range (Note 3) T
MIN
to T
MAX
LM34, LM34A −50˚F to +300˚F
LM34C, LM34CA −40˚F to +230˚F
LM34D +32˚F to +212˚F
DC Electrical Characteristics (Notes 2, 7)
LM34A LM34CA
Parameter Conditions Tested Design Tested Design Units
Typical Limit Limit Typical Limit Limit (Max)
(Note 5) (Note 6) (Note 5) (Note 6)
Accuracy (Note 8) T
A
= +77˚F ±0.4 ±1.0 ±0.4 ±1.0 ˚F
T
A
= 0˚F ±0.6 ±0.6 ±2.0 ˚F
T
A
=T
MAX
±0.8 ±2.0 ±0.8 ±2.0 ˚F
T
A
=T
MIN
±0.8 ±2.0 ±0.8 ±3.0 ˚F
Nonlinearity (Note 9) T
MIN
≤T
A
≤T
MAX
±0.35 ±0.7 ±0.30 ±0.6 ˚F
Sensor Gain T
MIN
≤T
A
≤T
MAX
+10.0 +9.9, +10.0 +9.9, mV/˚F, min
(Average Slope) +10.1 +10.1 mV/˚F, max
Load Regulation T
A
= +77˚F ±0.4 ±1.0 ±0.4 ±1.0 mV/mA
(Note 4) T
MIN
≤T
A
≤T
MAX
±0.5 ±3.0 ±0.5 ±3.0 mV/mA
0≤I
L
≤1mA
Line Regulation T
A
= +77˚F ±0.01 ±0.05 ±0.01 ±0.05 mV/V
(Note 4) 5V ≤V
S
≤30V ±0.02 ±0.1 ±0.02 ±0.1 mV/V
Quiescent Current V
S
= +5V, +77˚F 75 90 75 90 µA
(Note 10) V
S
= +5V 131 160 116 139 µA
V
S
= +30V, +77˚F 76 92 76 92 µA
V
S
= +30V 132 163 117 142 µA
Change of Quiescent 4V ≤V
S
≤30V, +77˚F +0.5 2.0 0.5 2.0 µA
Current (Note 4) 5V ≤V
S
≤30V +1.0 3.0 1.0 3.0 µA
Temperature Coefficient +0.30 +0.5 +0.30 +0.5 µA/˚F
of Quiescent Current
Minimum Temperature In circuit of
Figure 1
, +3.0 +5.0 +3.0 +5.0 ˚F
for Rated Accuracy I
L
=0
Long-Term Stability T
j
=T
MAX
for 1000 hours ±0.16 ±0.16 ˚F
Note 2: Unless otherwise noted, these specifications apply: −50˚F ≤Tj≤+ 300˚F for the LM34 and LM34A; −40˚F ≤Tj≤+230˚F for the LM34C and LM34CA; and
+32˚F ≤Tj≤+ 212˚F for the LM34D. VS= +5 Vdc and ILOAD = 50 µAin the circuit of
Figure 2
; +6 Vdc for LM34 and LM34Afor 230˚F ≤Tj≤300˚F. These specifications
also apply from +5˚F to TMAX in the circuit of
Figure 1
.
Note 3: Thermal resistance of the TO-46 package is 720˚F/W junction to ambient and 43˚F/W junction to case.Thermal resistance of the TO-92 package is 324˚F/W
junction to ambient. Thermal resistance of the small outline molded package is 400˚F/W junction to ambient. For additional thermal resistance information see table
in the Typical Applications section.
Note 4: 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 5: Tested limits are guaranteed and 100% tested in production.
Note 6: Design limits are guaranteed (but not 100% production tested) over the indicated temperature and supply voltage ranges. These limits are not used to
calculate outgoing quality levels.
Note 7: Specification in BOLDFACE TYPE apply over the full rated temperature range.
LM34
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DC Electrical Characteristics (Notes 2, 7) (Continued)
Note 8: Accuracy is defined as the error between the output voltage and 10 mV/˚F times the device’s case temperature at specified conditions of voltage, current,
and temperature (expressed in ˚F).
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: Quiescent current is defined in the circuit of
Figure 1
.
Note 11: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC andAC electrical specifications do not apply when operating
the device beyond its rated operating conditions (Note 2).
Note 12: Human body model, 100 pF discharged through a 1.5 kΩresistor.
Note 13: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National
Semiconductor Linear Data Book for other methods of soldering surface mount devices.
DC Electrical Characteristics (Notes 2, 7)
LM34 LM34C, LM34D
Parameter Conditions Tested Design Tested Design Units
Typical Limit Limit Typical Limit Limit (Max)
(Note 5) (Note 6) (Note 5) (Note 6)
Accuracy, LM34, LM34C T
A
= +77˚F ±0.8 ±2.0 ±0.8 ±2.0 ˚F
(Note 8) T
A
= 0˚F ±1.0 ±1.0 ±3.0 ˚F
T
A
=T
MAX
±1.6 ±3.0 ±1.6 ±3.0 ˚F
T
A
=T
MIN
±1.6 ±3.0 ±1.6 ±4.0 ˚F
Accuracy, LM34D T
A
= +77˚F ±1.2 ±3.0 ˚F
(Note 8) T
A
=T
MAX
±1.8 ±4.0 ˚F
T
A
=T
MIN
±1.8 ±4.0 ˚F
Nonlinearity (Note 9) T
MIN
≤T
A
≤T
MAX
±0.6 ±1.0 ±0.4 ±1.0 ˚F
Sensor Gain T
MIN
≤T
A
≤T
MAX
+10.0 +9.8, +10.0 +9.8, mV/˚F, min
(Average Slope) +10.2 +10.2 mV/˚F, max
Load Regulation T
A
= +77˚F ±0.4 ±2.5 ±0.4 ±2.5 mV/mA
(Note 4) T
MIN
≤T
A
≤+150˚F ±0.5 ±6.0 ±0.5 ±6.0 mV/mA
0≤I
L
≤1mA
Line Regulation T
A
= +77˚F ±0.01 ±0.1 ±0.01 ±0.1 mV/V
(Note 4) 5V ≤V
S
≤30V ±0.02 ±0.2 ±0.02 ±0.2 mV/V
Quiescent Current V
S
= +5V, +77˚F 75 100 75 100 µA
(Note 10) V
S
= +5V 131 176 116 154 µA
V
S
= +30V, +77˚F 76 103 76 103 µA
V
S
= +30V 132 181 117 159 µA
Change of Quiescent 4V ≤V
S
≤30V, +77˚F +0.5 3.0 0.5 3.0 µA
Current (Note 4) 5V ≤V
S
≤30V +1.0 5.0 1.0 5.0 µA
Temperature Coefficient +0.30 +0.7 +0.30 +0.7 µA/˚F
of Quiescent Current
Minimum Temperature In circuit of
Figure 1
, +3.0 +5.0 +3.0 +5.0 ˚F
for Rated Accuracy I
L
=0
Long-Term Stability T
j
=T
MAX
for 1000 hours ±0.16 ±0.16 ˚F
LM34
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Typical Performance Characteristics
Thermal Resistance
Junction to Air
DS006685-22
Thermal Time Constant
DS006685-23
Thermal Response in
Still Air
DS006685-24
Thermal Response in
Stirred Oil Bath
DS006685-25
Minimum Supply Voltage
vs. Temperature
DS006685-26
Quiescent Current vs.
Temperature
(In Circuit of
Figure 1
)
DS006685-27
Quiescent Current vs. Temp-
erature (In Circuit of
Figure 2
;
−V
S
= −5V, R1 = 100k)
DS006685-28
Accuracy vs. Temperature
(Guaranteed)
DS006685-29
Accuracy vs. Temperature
(Guaranteed)
DS006685-30
LM34
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Typical Performance Characteristics (Continued)
Typical Applications
The LM34 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or
cemented to a surface and its temperature will be within
about 0.02˚F 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 actual
temperature of the LM34 die would be at an intermediate
temperature between the surface temperature and the air
temperature. This is expecially true for the TO-92 plastic
package, where the copper leads are the principal thermal
path to carry heat into the device, so its temperature might
be closer to the air temperature than to the surface tempera-
ture.
To minimize this problem, be sure that the wiring to the
LM34, as it leaves the device, is held at the same tempera-
ture as the surface of interest. The easiest way to do this is
to cover up these wires with a bead of epoxy which will
insure that the leads and wires are all at the same tempera-
ture as the surface, and that the LM34 die’s temperature will
not be affected by the air temperature.
The TO-46 metal package can also be soldered to a metal
surface or pipe without damage. Of course in that case, the
V
−
terminal of the circuit will be grounded to that metal.
Alternatively, the LM34 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 LM34 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
insure that moisture cannot corrode the LM34 or its connec-
tions.
These devices are sometimes soldered to a small,
light-weight heat fin to decrease the thermal time constant
and speed up the response in slowly-moving air. On the
other hand, a small thermal mass may be added to the
sensor to give the steadiest reading despite small deviations
in the air temperature.
Capacitive Loads
Like most micropower circuits, the LM34 has a limited ability
to drive heavy capacitive loads. The LM34 by itself is able to
drive 50 pF without special precautions. If heavier loads are
anticipated, it is easy to isolate or decouple the load with a
resistor; see
Figure 3
. Or you can improve the tolerance of
capacitance with a series R-C damper from output to
ground; see
Figure 4
. When the LM34 is applied with a 499Ω
load resistor (as shown), it is relatively immune to wiring
capacitance because the capacitance forms a bypass from
ground to input, not on the output. However, as with any
linear circuit connected to wires in a hostile environment, its
performance can be affected adversely by intense electro-
magnetic sources such as relays, radio transmitters, motors
with arcing brushes, SCR’s 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 are often
useful. These are shown in the following circuits.
Noise Voltage
DS006685-31
Start-Up Response
DS006685-32
DS006685-6
LM34
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Typical Applications
Temperature Rise of LM34 Due to Self-Heating (Thermal Resistance)
Conditions TO-46, TO-46, TO-92, TO-92, SO-8 SO-8
No Heat
Sink Small Heat Fin
(Note 14) No Heat
Sink Small Heat Fin
(Note 15) No Heat
Sink Small Heat Fin
(Note 15)
Still air 720˚F/W 180˚F/W 324˚F/W 252˚F/W 400˚F/W 200˚F/W
Moving air 180˚F/W 72˚F/W 162˚F/W 126˚F/W 190˚F/W 160˚F/W
Still oil 180˚F/W 72˚F/W 162˚F/W 126˚F/W
Stirred oil 90˚F/W 54˚F/W 81˚F/W 72˚F/W
(Clamped to metal, (43˚F/W) (95˚F/W)
infinite heat sink)
Note 14: Wakefield type 201 or 1" disc of 0.020" sheet brass, soldered to case, or similar.
Note 15: TO-92 and SO-8 packages glued and leads soldered to 1" square of 1/16" printed circuit board with 2 oz copper foil, or similar.
DS006685-7
FIGURE 3. LM34 with Decoupling from Capacitive Load
DS006685-8
FIGURE 4. LM34 with R-C Damper
Two-Wire Remote Temperature Sensor
(Grounded Sensor)
DS006685-9
VOUT = 10mV/˚F (TA+3˚F)
FROM +3˚F TO + 100˚F
Two-Wire Remote Temperature Sensor
(Output Referred to Ground)
DS006685-10
LM34
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Typical Applications (Continued)
4-to-20 mA Current Source
(0 to +100˚F)
DS006685-11
Fahrenheit Thermometer
(Analog Meter)
DS006685-12
Expanded Scale Thermometer
(50˚ to 80˚ Fahrenheit, for Example Shown)
DS006685-13
Temperature-to-Digital Converter
(Serial Output, +128˚F Full Scale)
DS006685-14
LM34 with Voltage-to-Frequency Converter and Isolated Output
(3˚F to + 300˚F; 30 Hz to 3000 Hz)
DS006685-15
LM34
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Typical Applications (Continued)
Bar-Graph Temperature Display
(Dot Mode)
DS006685-16
*= 1% or 2% film resistor
—Trim RBfor VB= 3.525V
—Trim RCfor VC= 2.725V
—Trim RAfor VA= 0.085V + 40 mV/˚F x TAMBIENT
—Example, VA= 3.285V at 80˚F
Temperature-to-Digital Converter
(Parallel TRI-STATE®Outputs for Standard Data Bus to µP Interface, 128 ˚F Full Scale)
DS006685-17
LM34
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Typical Applications (Continued)
Block Diagram
Temperature Controller
DS006685-18
DS006685-19
LM34
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Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM34H, LM34AH, LM34CH,
LM34CAH or LM34DH
NS Package H03H
Order Number LM34DM
NS Package Number M08A
LM34
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
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accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
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support device or system whose failure to perform
can be reasonably expected to cause the failure of
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www.national.com
Order Number LM34CZ, LM34CAZ or LM34DZ
NS Package Z03A
LM34 Precision Fahrenheit 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.
