LM135,LM135A,LM235,LM235A,LM335,LM335A
LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors
Literature Number: SNIS160C
December 17, 2008
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 1Ω dy-
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 sensors
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 interfacing 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 tem-
perature range. The LM335 operates from −40°C to 100°C.
The LM135/LM235/LM335 are available packaged in hermet-
ic TO-46 transistor packages while the LM335 is also avail-
able in plastic TO-92 packages.
Features
■Directly calibrated in °Kelvin
■1°C initial accuracy available
■Operates from 400 μA to 5 mA
■Less than 1Ω dynamic impedance
■Easily calibrated
■Wide operating temperature range
■200°C overrange
■Low cost
Schematic Diagram
569801
© 2008 National Semiconductor Corporation 5698 www.national.com
LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors
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
8-Pin SOIC Package −65°C to 150°C
TO-92 Package −60°C to 150°C
TO-46 Package −60°C to 180°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)
8-Pin SOIC Package: 300°C
Vapor Phase (60 seconds): 215°C
Infrared (15 seconds): 220°C
TO-92 Package: 260°C
TO-46 Package: 300°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 TC = 25°C, IR = 1 mA 2.97 2.98 2.99 2.95 2.98 3.01 V
Uncalibrated Temperature Error TC = 25°C, IR = 1 mA 0.5 1 1 3 °C
Uncalibrated Temperature Error TMIN ≤ TC ≤ TMAX, IR = 1 mA 1.3 2.7 2 5 °C
Temperature Error with 25°C TMIN ≤ TC ≤ TMAX, IR = 1 mA 0.3 1 0.5 1.5 °C
Calibration
Calibrated Error at Extended TC = TMAX (Intermittent) 2 2 °C
Temperatures
Non-Linearity IR = 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 TC = 25°C, IR = 1 mA 2.95 2.98 3.01 2.92 2.98 3.04 V
Uncalibrated Temperature Error TC = 25°C, IR = 1 mA 1 3 2 6 °C
Uncalibrated Temperature Error TMIN ≤ TC ≤ TMAX, IR = 1 mA 2 5 4 9 °C
Temperature Error with 25°C TMIN ≤ TC ≤ TMAX, IR = 1 mA 0.5 1 1 2 °C
Calibration
Calibrated Error at Extended TC = TMAX (Intermittent) 2 2 °C
Temperatures
Non-Linearity IR = 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 ≤ IR ≤ 5 mA 2.5 10 3 14 mV
Change with Current At Constant Temperature
Dynamic Impedance IR = 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 TC = 125°C 0.2 0.2 °C/khr
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LM135/LM235/LM335, LM135A/LM235A/LM335A
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.
Thermal Resistance 8-Pin SOIC TO-92 TO-46
θJA (Junction to Ambient) 165°C/W 202°C/W 400°C/W
θJC (Junction to Case) N/A 170°C/W N/A
Note 4: Refer to RETS135H for military specifications.
Connection Diagrams
8-Pin SOIC
Surface Mount Package
569825
Top View
TO-92
Plastic Package
569808
Bottom View
TO-46
Metal Can Package*
569826
*Case is connected to negative pin
Bottom View
Ordering Information
Package Part Number Package Marking Transport Media NSC Drawing
8-Pin SOIC
LM335AM LM335AM 95 Units/Rail
M08A
LM335AMX 2.5k Units Tape and Reel
LM335M LM335M 95 Units/Rail
LM335MX 2.5k Units Tape and Reel
TO-92 LM335AZ LM335AZ 1800 Bag Z03Z
LM335Z LM335Z 1800 Bag
TO-46
LM135AH LM135AH 1000 Bag
H03H
LM135H LM135H 1000 Bag
LM235AH LM235AH 1000 Bag
LM235H LM235H 1000 Bag
LM335AH LM335AH 1000 Bag
LM335H LM335H 1000 Bag
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Typical Performance Characteristics
Reverse Voltage Change
569827
Calibrated Error
569828
Reverse Characteristics
569829
Response Time
569830
Dynamic Impedance
569831
Noise Voltage
569832
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Thermal Resistance Junction to Air
569833
Thermal Time Constant
569834
Thermal Response in Still Air
569835
Thermal Response in Stirred Oil Bath
569836
Forward Characteristics
569837
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Application Information
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 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 To is a reference
temperature, both expressed in degrees Kelvin. By calibrating
the output to read correctly at one temperature the output at
all temperatures is correct. Nominally the output is calibrated
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 pro-
portional to absolute temperature the same as scale factor
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 ½″ from
the end and the tubing heated above the melting point of the
core. The unfilled ½″ end melts and provides a seal over the
device.
Typical Applications
Basic Temperature Sensor
569802
Calibrated Sensor
569809
*Calibrate for 2.982V at 25°C
Wide Operating Supply
569810
Minimum Temperature Sensing
569804
Average Temperature Sensing
569818
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Remote Temperature Sensing
569819
Wire length for 1°C error due to wire drop
IR = 1 mA IR = 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
569820
Simple Temperature Controller
569805
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Simple Temperature Control
569821
Ground Referred Fahrenheit Thermometer
569822
*Adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
Centigrade Thermometer
569823
*Adjust for 2.7315V at output of LM308
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Fahrenheit Thermometer
569824
*To calibrate adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
THERMOCOUPLE COLD JUNCTION COMPENSATION
Compensation for Grounded Thermocouple
569806
*Select R3 for proper thermocouple type
THERMO- R3 SEEBECK
COUPLE (±1%) COEFFICIENT
J377Ω 52.3 μV/°C
T308Ω 42.8 μV/°C
K293Ω 40.8 μV/°C
S45.8Ω 6.4 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
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Single Power Supply Cold Junction Compensation
569811
*Select R3 and R4 for thermocouple type
THERMO- R3 R4 SEEBECK
COUPLE COEFFICIENT
J 1.05K 385Ω 52.3 μV/°C
T856Ω 315Ω 42.8 μV/°C
K816Ω 300Ω 40.8 μV/°C
S128Ω 46.3Ω 6.4 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
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Centigrade Calibrated Thermocouple Thermometer
569812
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
569813
†Adjust D1 to 50 mV greater VZ than D2.
Charge terminates on 5°C temperature rise. Couple D2 to battery.
Differential Temperature Sensor
569807
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Differential Temperature Sensor
569814
Variable Offset Thermometer‡
569815
†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
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Ground Referred Centigrade Thermometer
569816
Air Flow Detector*
569817
*Self heating is used to detect air flow
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 operating
output voltage and case temperature at 10 mV/°K over a tem-
perature range at a specified operating current with the 25°C
error adjusted to zero.
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LM135/LM235/LM335, LM135A/LM235A/LM335A
Physical Dimensions inches (millimeters) unless otherwise noted
8-Pin SOIC
NS Package Number M08A
TO-92
NS Package Z03A
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LM135/LM235/LM335, LM135A/LM235A/LM335A
TO-46
NS Package Number H03H
15 www.national.com
LM135/LM235/LM335, LM135A/LM235A/LM335A
Notes
LM135/LM235/LM335, LM135A/LM235A/LM335A Precision Temperature Sensors
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