LM135/LM235/LM335, LM135A/LM235A/LM335A
Precision Temperature Sensors
General Description
The LM135 series are precision, easily-calibrated, integrated
circuit temperature sensors. Operating as a 2-terminal zener,
the LM135 has a breakdown voltage directly proportional to
absolute temperature at +10 mV/˚K. With less than 1Ωdy-
namic impedance the device operates over a current range
of 400 µA to 5 mA with virtually no change in performance.
When calibrated at 25˚C the LM135 has typically less than
1˚C error over a 100˚C temperature range. Unlike other sen-
sors the LM135 has a linear output.
Applications for the LM135 include almost any type of tem-
perature sensing over a −55˚C to +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 −55˚C to +150˚C temperature
range while the LM235 operates over a −40˚C to +125˚C
temperature range. The LM335 operates from −40˚C to
+100˚C. The LM135/LM235/LM335 are available packaged
in hermetic TO-46 transistor packages while the LM335 is
also available in plastic TO-92 packages.
Features
nDirectly calibrated in ˚Kelvin
n1˚C initial accuracy available
nOperates from 400 µA to 5 mA
nLess than 1Ωdynamic impedance
nEasily calibrated
nWide operating temperature range
n200˚C overrange
nLow cost
Schematic Diagram
DS005698-1
May 1999
LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors
© 1999 National Semiconductor Corporation DS005698 www.national.com
Connection Diagrams
TO-92
Plastic Package
DS005698-8
Bottom View
Order Number LM335Z
or LM335AZ
See NS Package
Number Z03A
SO-8
Surface Mount Package
DS005698-25
Order Number LM335M
See NS Package
Number M08A
TO-46
Metal Can Package*
DS005698-26
*Case is connected to negative pin
Bottom View
Order Number LM135H,
LM135H-MIL, LM235H,
LM335H, LM135AH,
LM235AH or LM335AH
See NS Package
Number H03H
www.national.com 2
Absolute Maximum Ratings (Note 4)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Reverse Current 15 mA
Forward Current 10 mA
Storage Temperature
TO-46 Package −60˚C to +180˚C
TO-92 Package −60˚C to +150˚C
SO-8 Package −65˚C to +150˚C
Specified Operating Temp. Range
Continuous Intermittent
(Note 2)
LM135, LM135A −55˚C to +150˚C 150˚C to 200˚C
LM235, LM235A −40˚C to +125˚C 125˚C to 150˚C
LM335, LM335A −40˚C to +100˚C 100˚C to 125˚C
Lead Temp. (Soldering, 10 seconds)
TO-92 Package: 260˚C
TO-46 Package: 300˚C
SO-8 Package: 300˚C
Vapor Phase (60 seconds): 215˚C
Infrared (15 seconds): 220˚C
Temperature Accuracy (Note 1)
LM135/LM235, LM135A/LM235A
Parameter Conditions LM135A/LM235A LM135/LM235 Units
Min Typ Max Min Typ Max
Operating Output Voltage T
C
=25˚C, I
R
=1 mA 2.97 2.98 2.99 2.95 2.98 3.01 V
Uncalibrated Temperature Error T
C
=25˚C, I
R
=1 mA 0.5 1 1 3 ˚C
Uncalibrated Temperature Error T
MIN
≤T
C
≤T
MAX
,I
R
=1 mA 1.3 2.7 2 5 ˚C
Temperature Error with 25˚C T
MIN
≤T
C
≤T
MAX
,I
R
=1 mA 0.3 1 0.5 1.5 ˚C
Calibration
Calibrated Error at Extended T
C
=T
MAX
(Intermittent) 2 2 ˚C
Temperatures
Non-Linearity I
R
=1 mA 0.3 0.5 0.3 1 ˚C
Temperature Accuracy (Note 1)
LM335, LM335A
Parameter Conditions LM335A LM335 Units
Min Typ Max Min Typ Max
Operating Output Voltage T
C
=25˚C, I
R
=1 mA 2.95 2.98 3.01 2.92 2.98 3.04 V
Uncalibrated Temperature Error T
C
=25˚C, I
R
=1mA 1 3 2 6 ˚C
Uncalibrated Temperature Error T
MIN
≤T
C
≤T
MAX
,I
R
=1mA 2 5 4 9 ˚C
Temperature Error with 25˚C T
MIN
≤T
C
≤T
MAX
,I
R
=1 mA 0.5 1 1 2 ˚C
Calibration
Calibrated Error at Extended T
C
=T
MAX
(Intermittent) 2 2 ˚C
Temperatures
Non-Linearity I
R
=1 mA 0.3 1.5 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 µA≤I
R
≤5 mA 2.5 10 3 14 mV
Change with Current At Constant Temperature
Dynamic Impedance I
R
=1 mA 0.5 0.6 Ω
Output Voltage Temperature +10 +10 mV/˚C
Coefficient
Time Constant Still Air 80 80 sec
100 ft/Min Air 10 10 sec
Stirred Oil 1 1 sec
Time Stability T
C
=125˚C 0.2 0.2 ˚C/khr
www.national.com3
Electrical Characteristics (Note 1) (Continued)
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
θ
JA
(junction to ambient) 202˚C/W 400˚C/W 165˚C/W
θ
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
DS005698-27
Calibrated Error
DS005698-28
Reverse Characteristics
DS005698-29
Response Time
DS005698-30
Dynamic Impedance
DS005698-31
Noise Voltage
DS005698-32
Thermal Resistance
Junction to Air
DS005698-33
Thermal Time Constant
DS005698-34
Thermal Response in Still Air
DS005698-35
www.national.com 4
Typical Performance Characteristics (Continued)
Application Hints
CALIBRATING THE LM135
Included on the LM135 chip is an easy method of calibrating
the device for higher accuracies. Apot connected across the
LM135 with the arm tied to the adjustment terminal allows 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
(−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:
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 output
at all temperatures is correct. Nominally the output is cali-
brated at 10 mV/˚K.
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 resis-
tance 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 error
proportional to absolute temperature the same as scale fac-
tor errors.
WATERPROOFING SENSORS
Meltable inner core heat shrinkable tubing such as manufac-
tured by Raychem can be used to make low-cost waterproof
sensors. The LM335 is inserted into the tubing about
1
⁄
2
"
from the end and the tubing heated above the melting point
of the core. The unfilled
1
⁄
2
" end melts and provides a seal
over the device.
Typical Applications
Thermal Response in Stirred Oil Bath
DS005698-36
Forward Characteristics
DS005698-37
Basic Temperature Sensor
DS005698-2
Calibrated Sensor
DS005698-9
*Calibrate for 2.982V at 25˚C
Wide Operating Supply
DS005698-10
www.national.com5
Typical Applications (Continued)
Minimum Temperature Sensing
DS005698-4
Average Temperature Sensing
DS005698-18
Remote Temperature Sensing
DS005698-19
Wire length for 1˚C error due to wire drop
I
R
=1
mA I
R
=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 IR=0.5 mA, the trim pot must be deleted.
Isolated Temperature Sensor
DS005698-20
www.national.com 6
Typical Applications (Continued)
Simple Temperature Controller
DS005698-5
Simple Temperature Control
DS005698-21
Ground Referred Fahrenheit Thermometer
DS005698-22
*Adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
Centigrade Thermometer
DS005698-23
*Adjust for 2.7315V at output of LM308
www.national.com7
Typical Applications (Continued)
Fahrenheit Thermometer
DS005698-24
*To calibrate adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
THERMOCOUPLE COLD JUNCTION COMPENSATION
Compensation for Grounded Thermocouple
DS005698-6
*Select R3 for proper thermocouple type
THERMO- R3 SEEBECK
COUPLE (±1%) COEFFICIENT
J 377Ω52.3 µV/˚C
T 308Ω42.8 µV/˚C
K 293Ω40.8 µV/˚C
S 45.8Ω6.4 µV/˚C
Adjustments: Compensates for both sensor and resistor tolerances
1. Short LM329B
2. Adjust R1 for Seebeck Coefficient times ambient temperature (in degrees K) across R3.
3. Short LM335 and adjust R2 for voltage across R3 corresponding to thermocouple type
J 14.32 mV K 11.17 mV
T 11.79 mV S 1.768 mV
www.national.com 8
Typical Applications (Continued)
Single Power Supply Cold Junction Compensation
DS005698-11
*Select R3 and R4 for thermocouple type
THERMO- R3 R4 SEEBECK
COUPLE COEFFICIENT
J 1.05K 385Ω52.3 µV/˚C
T 856Ω315Ω42.8 µV/˚C
K 816Ω300Ω40.8 µV/˚C
S 128Ω46.3Ω6.4 µV/˚C
Adjustments:
1. Adjust R1 for the voltage across R3 equal to the Seebeck Coefficient times ambient temperature in degrees Kelvin.
2. Adjust R2 for voltage across R4 corresponding to thermocouple
J 14.32 mV
T 11.79 mV
K 11.17 mV
S 1.768 mV
www.national.com9
Typical Applications (Continued)
Centigrade Calibrated Thermocouple Thermometer
DS005698-12
Terminate thermocouple reference junction in close proximity to LM335.
Adjustments:
1. Apply signal in place of thermocouple and adjust R3 for a gain of 245.7.
2. Short non-inverting input of LM308A and output of LM329B to ground.
3. Adjust R1 so that VOUT =2.982V @25˚C.
4. Remove short across LM329B and adjust R2 so that VOUT =246 mV @25˚C.
5. Remove short across thermocouple.
Fast Charger for Nickel-Cadmium Batteries
DS005698-13
†Adjust D1 to 50 mV greater VZthan D2.
Charge terminates on 5˚C temperature rise. Couple D2 to battery.
Differential Temperature Sensor
DS005698-7
www.national.com 10
Typical Applications (Continued)
Differential Temperature Sensor
DS005698-14
Variable Offset Thermometer‡
DS005698-15
†Adjust for zero with sensor at 0˚C and 10T pot set at 0˚C
*Adjust for zero output with 10T pot set at 100˚C and sensor at 100˚C
‡Output reads difference between temperature and dial setting of 10T pot
www.national.com11
Typical Applications (Continued)
Definition of Terms
Operating Output Voltage: The voltage appearing across
the positive and negative terminals of the device at specified
conditions of operating temperature and current.
Uncalibrated Temperature Error: The error between the
operating output voltage at 10 mV/˚K and case temperature
at specified conditions of current and case temperature.
Calibrated Temperature Error: The error between operat-
ing output voltage and case temperature at 10 mV/˚K over a
temperature range at a specified operating current with the
25˚C error adjusted to zero.
Ground Referred Centigrade Thermometer
DS005698-16
Air Flow Detector*
DS005698-17
*Self heating is used to detect air flow
www.national.com 12
Physical Dimensions inches (millimeters) unless otherwise noted
Metal Can Package (H)
Order Number LM135H, LM235H, LM335H, LM135AH, LM235AH or LM335AH
NS Package Number H03H
8-Lead Molded Small Outline Package (M)
Order Number LM335M
NS Package Number M08A
www.national.com13
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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) 1 80-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: sea.support@nsc.com
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
Plastic Package
Order Number LM335Z or LM335AZ
NS Package Z03A
LM135/LM235/LM335, LM135A/LM235A/LM335A Precision 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.
