LM135.PDF

February 1995

LM135/LM235/LM335, LM135A/LM235A/LM335A

Precision Temperature Sensors

General Description

The LM135 series are precision, easily-calibrated, integrat-

ed circuit temperature sensors. Operating as a 2-terminal

zener, the LM135 has a breakdown voltage directly propor-

tional to absolute temperature at a 10 mV/ § K. With less

than 1 X dynamic impedance the device operates over a

current range of 400 m A to 5 mA with virtually no change in

performance. When calibrated at 25 § C the LM135 has typi-

cally less than 1 § C error over a 100 § C temperature range.

Unlike other sensors the LM135 has a linear output.

Applications for the LM135 include almost any type of tem-

perature sensing over a b 55 § Cto a 150 § C temperature

range. The low impedance and linear output make interfac-

ing to readout or control circuitry especially easy.

The LM135 operates over a b 55 § Cto a 150 § C temperature

range while the LM235 operates over a b 40 § Cto a 125 § C

temperature range. The LM335 operates from b 40 § Cto

a 100 § C. The LM135/LM235/LM335 are available pack-

aged in hermetic TO-46 transistor packages while the

LM335 is also available in plastic TO-92 packages.

Features

Y Directly calibrated in § Kelvin

Y 1 § C initial accuracy available

Y Operates from 400 m Ato5mA

Y Less than 1 X dynamic impedance

Y Easily calibrated

Y Wide operating temperature range

Y 200 § C overrange

Y Low cost

Schematic Diagram

TL/H/5698±1

Connection Diagrams

TO-92

Plastic Package

SO-8

Surface Mount Package

TO-46

Metal Can Package*

TL/H/5698±8

Bottom View

Order Number LM335Z or LM335AZ

See NS Package Number Z03A

TL/H/5698±26

TL/H/5698±25

Order Number LM335M or

LM335AM

See NS Package Number M08A

Bottom View

*Case is connected to negative pin

Order Number LM135H,

LM135H-MIL, LM235H, LM335H,

LM135AH, LM235AH or LM335AH

See NS Package Number H03H

C 1995 National Semiconductor Corporation

TL/H/5698

RRD-B30M115/Printed in U. S. A.

Absolute Maximum Ratings

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales

Office/Distributors for availability and specifications.

(Note 4)

Reverse Current

Specified Operating Temp. Range

15 mA

Intermittent

Continuous (Note 2)

LM135, LM135A b 55 § Cto a 150 § C 150 § Cto200 § C

LM235, LM235A b 40 § Cto a 125 § C 125 § Cto150 § C

LM335, LM335A b 40 § Cto a 100 § C 100 § Cto125 § C

Lead Temp. (Soldering, 10 seconds)

TO-92 Package:

Forward Current

10 mA

Storage Temperature

TO-46 Package

b 60 § Cto a 180 § C

260 § C

TO-92 Package

b 60 § Cto a 150 § C

TO-46 Package:

300 § C

SO-8 Package

b 65 § Cto a 150 § C

SO-8 Package:

300 § C

Vapor Phase (60 seconds)

215 § C

Infrared (15 seconds)

220 § C

Temperature Accuracy LM135/LM235, LM135A/LM235A (Note 1)

Parameter

Conditions

LM135A/LM235A

LM135/LM235

Units

Min Typ Max Min Typ Max

Operating Output Voltage

T C e 25 § C, I R e 1 mA

2.97 2.98 2.99 2.95 2.98 3.01 V

Uncalibrated Temperature Error T C e 25 § C, I R e 1 mA

0.5

§ C

Uncalibrated Temperature Error T MIN s T C s T MAX ,I R e 1 mA

1.3 2.7

§ C

Temperature Error with 25 § C

T MIN s T C s T MAX ,I R e 1 mA

0.3

0.5 1.5

§ C

Calibration

Calibrated Error at Extended

T C e T MAX (Intermittent)

§ C

Temperatures

Non-Linearity

I R e 1 mA

0.3 0.5

0.3

§ C

Temperature Accuracy LM335, LM335A (Note 1)

Parameter

Conditions

LM335A

LM335

Units

Min Typ Max Min Typ Max

Operating Output Voltage

T C e 25 § C, I R e 1 mA

2.95 2.98 3.01 2.92 2.98 3.04 V

Uncalibrated Temperature Error T C e 25 § C, I R e 1mA

1 3

2 6 § C

Uncalibrated Temperature Error T MIN s T C s T MAX ,I R e 1mA

2 5

4 9 § C

Temperature Error with 25 § C

T MIN s T C s T MAX ,I R e 1 mA

0.5

§ C

Calibration

Calibrated Error at Extended

T C e T MAX (Intermittent)

§ C

Temperatures

Non-Linearity

I R e 1 mA

0.3 1.5

§ C

Electrical Characteristics (Note 1)

LM135/LM235

LM335

Parameter

Conditions

LM135A/LM235A

LM335A

Units

Min Typ Max Min Typ Max

Operating Output Voltage

400 m A s I R s 5 mA

2.5

14 mV

Change with Current

At Constant Temperature

Dynamic Impedance

I R e 1 mA

0.5

0.6

Output Voltage Temperature

a 10

mV/ § C

Coefficient

Time Constant

Still Air

sec

100 ft/Min Air

sec

Stirred Oil

sec

Time Stability

T C e 125 § C

0.2

§ C/khr

Note 1: Accuracy measurements are made in a well-stirred oil bath. For other conditions, self heating must be considered.

Note 2: Continuous operation at these temperatures for 10,000 hours for H package and 5,000 hours for Z package may decrease life expectancy of the device.

Note 3: Thermal Resistance TO-92 TO-46 SO-8

i JA (junction to ambient) 202 § C/W 400 § C/W 165 § C/W

i JC (junction to case)

170 § C/W N/A

N/A

Note 4: Refer to RETS135H for military specifications.

Typical Performance Characteristics

Reverse Voltage Change

Calibrated Error

Reverse Characteristics

Response Time

Dynamic Impedance

Noise Voltage

Thermal Resistance

Junction to Air

Thermal Time Constant

Thermal Response

in Still Air

Thermal Response in

Stirred Oil Bath

Forward Characteristics

TL/H/5698±3

Application Hints

CALIBRATING THE LM135

Included on the LM135 chip is an easy method of calibrating

the device for higher accuracies. A pot connected across

the LM135 with the arm tied to the adjustment terminal al-

lows a 1-point calibration of the sensor that corrects for

inaccuracy over the full temperature range.

This single point calibration works because the output of the

LM135 is proportional to absolute temperature with the ex-

trapolated output of sensor going to 0V output at 0 § K

( b 273. 15 § C). Errors in output voltage versus temperature

are only slope (or scale factor) errors so a slope calibration

at one temperature corrects at all temperatures.

The output of the device (calibrated or uncalibrated) can be

expressed as:

To insure good sensing accuracy several precautions must

be taken. Like any temperature sensing device, self heating

can reduce accuracy. The LM135 should be operated at the

lowest current suitable for the application. Sufficient current,

of course, must be available to drive both the sensor and

the calibration pot at the maximum operating temperature

as well as any external loads.

If the sensor is used in an ambient where the thermal resist-

ance is constant, self heating errors can be calibrated out.

This is possible if the device is run with a temperature stable

current. Heating will then be proportional to zener voltage

and therefore temperature. This makes the self heating er-

ror proportional to absolute temperature the same as scale

factor errors.

WATERPROOFING SENSORS

Meltable inner core heat shrinkable tubing such as manu-

factured by Raychem can be used to make low-cost water-

proof sensors. The LM335 is inserted into the tubing about

(/2 × from the end and the tubing heated above the melting

point of the core. The unfilled (/2 × end melts and provides a

seal over the device.

T o

where T is the unknown temperature and T o is a reference

temperature, both expressed in degrees Kelvin. By calibrat-

ing the output to read correctly at one temperature the out-

put at all temperatures is correct. Nominally the output is

calibrated at 10 mV/ § K.

Typical Applications

Basic Temperature Sensor

Calibrated Sensor

Wide Operating Supply

TL/H/5698±2

TL/H/5698±9

*Calibrate for 2.982V at 25 § C

TL/H/5698±10

Minimum Temperature Sensing

Average Temperature Sensing

Remote Temperature Sensing

TL/H/5698±4

TL/H/5698±19

TL/H/5698±18

Wire length for 1 § C error due to wire drop

I R e 1mA I R e 0.5 mA*

AWG FEET FEET

14 4000 8000

16 2500 5000

18 1600 3200

20 1000 2000

22 625 1250

24 400 800

*For I R e 0.5 mA, the trim pot must be deleted.

V OUT T e V OUT T o c

Typical Applications (Continued)

Isolated Temperature Sensor

TL/H/5698±20

Simple Temperature Controller

TL/H/5698±5

Simple Temperature Control

TL/H/5698±21

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