May 1999
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/ÊK. With less than 1Ω dynamic impedance the device operates over a current range of 400 µA to 5 mA with virtually no change in performance. When calibrated at 25ÊC the LM135 has typically less than 1ÊC error over a 100ÊC temperature range. Unlike other sensors the LM135 has a linear output.
Applications for the LM135 include almost any type of temperature sensing over a −55ÊC to +150ÊC temperature range. The low impedance and linear output make interfacing to readout or control circuitry especially easy.
The LM135 operates over a −55ÊC to +150ÊC temperature range while the LM235 operates over a −40ÊC to +125ÊC
temperature range. The LM335 operates from −40ÊC to +100ÊC. 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 ÊKelvin
n1ÊC initial accuracy available
nOperates from 400 µA to 5 mA
nLess than 1Ω dynamic impedance
nEasily calibrated
nWide operating temperature range
n200ÊC overrange
nLow cost
Schematic Diagram
DS005698-1
Sensors Temperature Precision LM135A/LM235A/LM335A LM135/LM235/LM335,
© 1999 National Semiconductor Corporation |
DS005698 |
www.national.com |
Connection Diagrams
TO-92 |
SO-8 |
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Plastic Package |
TO-46 |
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Surface Mount Package |
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Metal Can Package* |
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DS005698-8
Bottom View |
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DS005698-26 |
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Order Number LM335Z |
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DS005698-25 |
*Case is connected to negative pin |
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or LM335AZ |
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Order Number LM335M |
Bottom View |
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See NS Package |
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See NS Package |
Order Number LM135H, |
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Number Z03A |
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Number M08A |
LM135H-MIL, LM235H, |
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LM335H, LM135AH, |
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LM235AH or LM335AH |
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See NS Package |
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Number H03H |
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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 |
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TO-46 Package |
−60ÊC to +180ÊC |
TO-92 Package |
−60ÊC to +150ÊC |
SO-8 Package |
−65ÊC to +150ÊC |
Specified Operating Temp. Range |
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Continuous |
Intermittent |
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(Note 2) |
LM135, LM135A |
−55ÊC to +150ÊC |
150ÊC to 200ÊC |
LM235, LM235A |
−40ÊC to +125ÊC |
125ÊC to 150ÊC |
LM335, LM335A |
−40ÊC to +100ÊC |
100ÊC to 125ÊC |
Lead Temp. (Soldering, 10 seconds) |
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TO-92 Package: |
260ÊC |
TO-46 Package: |
300ÊC |
SO-8 Package: |
300ÊC |
Vapor Phase (60 seconds): |
215ÊC |
Infrared (15 seconds): |
220ÊC |
Temperature Accuracy (Note 1)
LM135/LM235, LM135A/LM235A
Parameter |
Conditions |
LM135A/LM235A |
LM135/LM235 |
Units |
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Min |
Typ |
Max |
Min |
Typ |
Max |
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Operating Output Voltage |
TC = 25ÊC, IR = 1 mA |
2.97 |
2.98 |
2.99 |
2.95 |
2.98 |
3.01 |
V |
Uncalibrated Temperature Error |
TC = 25ÊC, IR = 1 mA |
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0.5 |
1 |
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1 |
3 |
ÊC |
Uncalibrated Temperature Error |
TMIN ≤ TC ≤ TMAX, IR = 1 mA |
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1.3 |
2.7 |
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2 |
5 |
ÊC |
Temperature Error with 25ÊC |
TMIN ≤ TC ≤ TMAX, IR = 1 mA |
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0.3 |
1 |
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0.5 |
1.5 |
ÊC |
Calibration |
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Calibrated Error at Extended |
TC = TMAX (Intermittent) |
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2 |
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2 |
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ÊC |
Temperatures |
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Non-Linearity |
IR = 1 mA |
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0.3 |
0.5 |
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0.3 |
1 |
ÊC |
Temperature Accuracy (Note 1)
LM335, LM335A
Parameter |
Conditions |
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LM335A |
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LM335 |
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Units |
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Min |
Typ |
Max |
Min |
Typ |
Max |
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Operating Output Voltage |
TC = 25ÊC, IR = 1 mA |
2.95 |
2.98 |
3.01 |
2.92 |
2.98 |
3.04 |
V |
Uncalibrated Temperature Error |
TC = 25ÊC, IR = 1 mA |
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1 |
3 |
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2 |
6 |
ÊC |
Uncalibrated Temperature Error |
TMIN ≤ TC ≤ TMAX, IR = 1 mA |
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2 |
5 |
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4 |
9 |
ÊC |
Temperature Error with 25ÊC |
TMIN ≤ TC ≤ TMAX, IR = 1 mA |
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0.5 |
1 |
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1 |
2 |
ÊC |
Calibration |
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Calibrated Error at Extended |
TC = TMAX (Intermittent) |
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2 |
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2 |
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ÊC |
Temperatures |
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Non-Linearity |
IR = 1 mA |
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0.3 |
1.5 |
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0.3 |
1.5 |
ÊC |
Electrical Characteristics (Note 1)
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LM135/LM235 |
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LM335 |
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Parameter |
Conditions |
LM135A/LM235A |
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LM335A |
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Units |
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Min |
Typ |
Max |
Min |
Typ |
Max |
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Operating Output Voltage |
400 µA≤IR≤5 mA |
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2.5 |
10 |
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3 |
14 |
mV |
Change with Current |
At Constant Temperature |
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Dynamic Impedance |
IR=1 mA |
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0.5 |
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0.6 |
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Ω |
Output Voltage Temperature |
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+10 |
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+10 |
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mV/ÊC |
Coefficient |
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Time Constant |
Still Air |
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80 |
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80 |
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sec |
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100 ft/Min Air |
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10 |
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10 |
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sec |
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Stirred Oil |
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1 |
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1 |
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sec |
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Time Stability |
TC=125ÊC |
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0.2 |
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0.2 |
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ÊC/khr |
3 |
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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 |
θJA (junction to ambient) |
202ÊC/W |
400ÊC/W |
165ÊC/W |
θJC (junction to case) |
170ÊC/W |
N/A |
N/A |
Note 4: Refer to RETS135H for military specifications.
Typical Performance Characteristics
Reverse Voltage Change Calibrated Error Reverse Characteristics
DS005698-27 |
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DS005698-28 |
DS005698-29 |
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Response Time |
Dynamic Impedance |
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Noise Voltage |
DS005698-30 DS005698-31 DS005698-32
Thermal Resistance |
Thermal Time Constant |
Thermal Response in Still Air |
Junction to Air |
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DS005698-34 |
DS005698-35 |
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DS005698-33
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4 |
Typical Performance Characteristics (Continued)
Thermal Response in Stirred Oil Bath |
Forward Characteristics |
DS005698-36
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 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 extrapolated output of sensor going to 0V output at 0ÊK (−273.15ÊC). 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/ÊK.
DS005698-37
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 resistance 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 factor errors.
WATERPROOFING SENSORS
Meltable inner core heat shrinkable tubing such as manufactured 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
Basic Temperature Sensor |
Calibrated Sensor |
Wide Operating Supply |
DS005698-2
DS005698-9
*Calibrate for 2.982V at 25ÊC
DS005698-10
5 |
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