LM35.PDF

December 1994

LM35/LM35A/LM35C/LM35CA/LM35D

Precision Centigrade Temperature Sensors

General Description

The LM35 series are precision integrated-circuit tempera-

ture sensors, whose output voltage is linearly proportional to

the Celsius (Centigrade) temperature. The LM35 thus has

an advantage over linear temperature sensors calibrated in §

Kelvin, as the user is not required to subtract a large con-

stant voltage from its output to obtain convenient Centi-

grade scaling. The LM35 does not require any external cali-

bration or trimming to provide typical accuracies of g (/4 § C

at room temperature and g */4 § C over a full b 55 to a 150 § C

temperature range. Low cost is assured by trimming and

calibration at the wafer level. The LM35's low output imped-

ance, 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 60 m A from its supply, it has

very low self-heating, less than 0.1 § C in still air. The LM35 is

rated to operate over a b 55 § to a 150 § C temperature

range, while the LM35C is rated for a b 40 § to a 110 § C

range ( b 10 § with improved accuracy). The LM35 series is

available packaged in hermetic TO-46 transistor packages,

while the LM35C, LM35CA, and LM35D are also available in

the plastic TO-92 transistor package. The LM35D is also

available in an 8-lead surface mount small outline package

and a plastic TO-202 package.

Features

Y Calibrated directly in § Celsius (Centigrade)

Y Linear a 10.0 mV/ § C scale factor

Y 0.5 § C accuracy guaranteeable (at a 25 § C)

Y Rated for full b 55 § to a 150 § C range

Y Suitable for remote applications

Y Low cost due to wafer-level trimming

Y Operates from 4 to 30 volts

Y Less than 60 m A current drain

Y Low self-heating, 0.08 § C in still air

Y Nonlinearity only g (/4 § C typical

Y Low impedance output, 0.1 X for 1 mA load

Connection Diagrams

TO-46

Metal Can Package*

TO-92

Plastic Package

SO-8

Small Outline Molded Package

TL/H/5516±2

TL/H/5516±1

*Case is connected to negative pin (GND)

TL/H/5516±21

Order Number LM35CZ,

LM35CAZ or LM35DZ

See NS Package Number Z03A

Top View

N.C. e No Connection

Order Number LM35H, LM35AH,

LM35CH, LM35CAH or LM35DH

See NS Package Number H03H

Order Number LM35DM

See NS Package Number M08A

TO-202

Plastic Package

Typical Applications

TL/H/5516±3

FIGURE 1. Basic Centigrade

Temperature

Sensor ( a 2 § Cto a 150 § C)

TL/H/5516±4

Choose R 1 eb V S /50 m A

V OUT ea 1,500 mV at a 150 § C

ea 250 mV at a 25 § C

eb 550 mV at b 55 § C

FIGURE 2. Full-Range Centigrade

Temperature Sensor

TL/H/5516±24

Order Number LM35DP

See NS Package Number P03A

TRI-STATE É is a registered trademark of National Semiconductor Corporation.

C 1995 National Semiconductor Corporation

TL/H/5516

RRD-B30M75/Printed in U. S. A.

Absolute Maximum Ratings (Note 10)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales

Office/Distributors for availability and specifications.

Supply Voltage a 35V to b 0.2V

Output Voltage a 6V to b 1.0V

Output Current 10 mA

Storage Temp., TO-46 Package, b 60 § Cto a 180 § C

TO-92 Package, b 60 § Cto a 150 § C

SO-8 Package, b 65 § Cto a 150 § C

TO-202 Package, b 65 § Cto a 150 § C

SO Package (Note 12):

Vapor Phase (60 seconds) 215 § C

Infrared (15 seconds) 220 § C

ESD Susceptibility (Note 11) 2500V

Specified Operating Temperature Range: T MIN to T MAX

(Note 2)

LM35, LM35A

b 55 § Cto a 150 § C

LM35C, LM35CA

b 40 § Cto a 110 § C

LM35D

0 § Cto a 100 § C

Lead Temp.:

TO-46 Package, (Soldering, 10 seconds) 300 § C

TO-92 Package, (Soldering, 10 seconds) 260 § C

TO-202 Package, (Soldering, 10 seconds) a 230 § C

Electrical Characteristics (Note 1) (Note 6)

LM35A

LM35CA

Parameter

Conditions

Tested Design

Tested Design Units

Typical Limit

Limit Typical Limit

Limit

(Max.)

(Note 4) (Note 5)

Accuracy

T A ea 25 § C

g 0.2

g 0.5

g 0.2

g 0.5

§ C

(Note 7)

T A eb 10 § C

g 0.3

g 1.0

§ C

T A e T MAX

g 0.4

g 1.0

g 0.4

g 1.0

§ C

T A e T MIN

g 0.4 g 1.0

g 0.4

g 1.5

§ C

Nonlinearity

T MIN s T A s T MAX g 0.18

g 0.35 g 0.15

g 0.3 § C

(Note 8)

Sensor Gain

T MIN s T A s T MAX a 10.0 a 9.9,

a 10.0

a 9.9, mV/ § C

(Average Slope)

a 10.1

Load Regulation

T A ea 25 § C

g 0.4 g 1.0

mV/mA

(Note 3) 0 s I L s 1mA T MIN s T A s T MAX g 0.5

g 3.0 g 0.5

g 3.0 mV/mA

Line Regulation

T A ea 25 § C

g 0.01 g 0.05

mV/V

(Note 3)

4V s V S s 30V

g 0.02

g 0.1 g 0.02

g 0.1 mV/V

Quiescent Current

V S ea 5V, a 25 § C

m A

(Note 9)

V S ea 5V

105

131 91

114 m A

V S ea 30V, a 25 § C 56.2

56.2

m A

V S ea 30V

105.5

133 91.5

116 m A

Change of

4V s V S s 30V, a 25 § C 0.2

1.0

0.2

1.0

m A

Quiescent Current

4V s V S s 30V

0.5

2.0 0.5

2.0

m A

(Note 3)

Temperature

a 0.39

a 0.5 a 0.39

a 0.5 m A/ § C

Coefficient of

Quiescent Current

Minimum Temperature In circuit of

a 1.5

a 2.0 a 1.5

a 2.0

§ C

for Rated Accuracy Figure1,I L e 0

Long Term Stability

T J e T MAX , for

g 0.08

§ C

1000 hours

Note 1: Unless otherwise noted, these specifications apply: b 55 § C s T J s a 150 § C for the LM35 and LM35A; b 40 § s T J s a 110 § C for the LM35C and LM35CA; and

0 § s T J s a 100 § C for the LM35D. V S ea 5Vdc and I LOAD e 50 m A, in the circuit of Figure2. These specifications also apply from a 2 § CtoT MAX in the circuit of

Figure1. Specifications in boldface apply over the full rated temperature range.

Note 2: Thermal resistance of the TO-46 package is 400 § C/W, junction to ambient, and 24 § C/W junction to case. Thermal resistance of the TO-92 package is

180 § C/W junction to ambient. Thermal resistance of the small outline molded package is 220 § C/W junction to ambient. Thermal resistance of the TO-202 package

is 85 § C/W junction to ambient. For additional thermal resistance information see table in the Applications section.

Electrical Characteristics (Note 1) (Note 6) (Continued)

LM35

LM35C, LM35D

Parameter

Conditions

Tested Design

Tested Design Units

Typical Limit

Limit Typical Limit

Limit

(Max.)

(Note 4) (Note 5)

Accuracy,

T A ea 25 § C

g 0.4

g 1.0

g 0.4

g 1.0

§ C

LM35, LM35C

T A eb 10 § C

g 0.5

g 1.5

§ C

(Note 7)

T A e T MAX

g 0.8

g 1.5

g 0.8

g 1.5

§ C

T A e T MIN

g 0.8

g 1.5 g 0.8

g 2.0

§ C

Accuracy,

T A ea 25 § C

g 0.6 g 1.5

§ C

LM35D

T A e T MAX

g 0.9

g 2.0

§ C

(Note 7)

T A e T MIN

g 0.9

g 2.0

§ C

Nonlinearity

T MIN s T A s T MAX g 0.3

g 0.5 g 0.2

g 0.5 § C

(Note 8)

Sensor Gain

T MIN s T A s T MAX a 10.0 a 9.8,

a 10.0

a 9.8, mV/ § C

(Average Slope)

a 10.2

Load Regulation

T A ea 25 § C

g 0.4

g 2.0

g 0.4

g 2.0

mV/mA

(Note 3) 0 s I L s 1mA T MIN s T A s T MAX g 0.5

g 5.0 g 0.5

g 5.0 mV/mA

Line Regulation

T A ea 25 § C

g 0.01 g 0.1

mV/V

(Note 3)

4V s V S s 30V

g 0.02

g 0.2 g 0.02

g 0.2 mV/V

Quiescent Current

V S ea 5V, a 25 § C

m A

(Note 9)

V S ea 5V

105

158 91

138 m A

V S ea 30V, a 25 § C 56.2

56.2

m A

V S ea 30V

105.5

161 91.5

141 m A

Change of

4V s V S s 30V, a 25 § C 0.2

2.0

0.2

2.0

m A

Quiescent Current

4V s V S s 30V

0.5

3.0 0.5

3.0

m A

(Note 3)

Temperature

a 0.39

a 0.7 a 0.39

a 0.7 m A/ § C

Coefficient of

Quiescent Current

Minimum Temperature In circuit of

a 1.5

a 2.0 a 1.5

a 2.0

§ C

for Rated Accuracy Figure1,I L e 0

Long Term Stability

T J e T MAX , for

g 0.08

§ C

1000 hours

Note 3: 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 4: Tested Limits are guaranteed and 100% tested in production.

Note 5: 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 6: Specifications in boldface apply over the full rated temperature range.

Note 7: Accuracy is defined as the error between the output voltage and 10mv/ § C times the device's case temperature, at specified conditions of voltage, current,

and temperature (expressed in § C).

Note 8: 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 9: Quiescent current is defined in the circuit of Figure1.

Note 10: 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. See Note 1.

Note 11: Human body model, 100 pF discharged through a 1.5 k X resistor.

Note 12: 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.

Typical Performance Characteristics

Thermal Resistance

Junction to Air

Thermal Time Constant

Thermal Response

in Still Air

Thermal Response in

Stirred Oil Bath

Minimum Supply

Voltage vs. Temperature

Quiescent Current

vs. Temperature

(In Circuit of Figure1.)

TL/H/5516±17

Quiescent Current

vs. Temperature

(In Circuit of Figure2.)

Accuracy vs. Temperature

(Guaranteed)

Accuracy vs. Temperature

(Guaranteed)

TL/H/5516±18

Noise Voltage

Start-Up Response

TL/H/5516±22

Applications

The LM35 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 0.01 § 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 actual temperature of the LM35 die would be at an inter-

mediate 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 tempera-

ture might be closer to the air temperature than to the sur-

face temperature.

To minimize this problem, be sure that the wiring to the

LM35, 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 LM35 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 b terminal of the circuit will be grounded to that metal.

Alternatively, the LM35 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 LM35 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 var-

nishes such as Humiseal and epoxy paints or dips are often

used to insure that moisture cannot corrode the LM35 or its

connections.

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.

Temperature Rise of LM35 Due To Self-heating (Thermal Resistance)

TO-46, TO-46, TO-92, TO-92, SO-8 SO-8 TO-202 TO-202 ***

no heat sink small heat fin* no heat sink small heat fin** no heat sink small heat fin** no heat sink small heat fin

Still air

400 § C/W 100 § C/W 180 § C/W 140 § C/W 220 § C/W 110 § C/W 85 § C/W 60 § C/W

Moving air

100 § C/W 40 § C/W 90 § C/W 70 § C/W 105 § C/W 90 § C/W 25 § C/W 40 § C/W

Still oil

100 § C/W 40 § C/W 90 § C/W 70 § C/W

Stirred oil

50 § C/W 30 § C/W 45 § C/W 40 § C/W

(Clamped to metal,

Infinite heat sink)

(24 § C/W)

(55 § C/W)

(23 § C/W)

* Wakefield type 201, or 1 × disc of 0.020 × sheet brass, soldered to case, or similar.

** TO-92 and SO-8 packages glued and leads soldered to 1 × square of (/16 × printed circuit board with 2 oz. foil or similar.

Typical Applications (Continued)

TL/H/5516±19

FIGURE 3. LM35 with Decoupling from Capacitive Load

TL/H/5516±20

FIGURE 4. LM35 with R-C Damper

CAPACITIVE LOADS

Like most micropower circuits, the LM35 has a limited ability

to drive heavy capacitive loads. The LM35 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 Figure3. Or you can improve the tolerance of

capacitance with a series R-C damper from output to

ground; see Figure4.

When the LM35 is applied with a 200 X load resistor as

shown in Figure5,6, or 8, 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 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 capac-

itor from V IN to ground and a series R-C damper such as

75 X in series with 0.2 or 1 m F from output to ground are

often useful. These are shown in Figures13,14, and 16.

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