SNIS160E May   1999  – February 2015 LM135 , LM135A , LM235 , LM235A , LM335 , LM335A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Conditions
    3. 6.3 Thermal Information
    4. 6.4 Temperature Accuracy: LM135/LM235, LM135A/LM235A
    5. 6.5 Temperature Accuracy: LM335, LM335A
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Temperature Calibration Using ADJ Pin
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
    3. 8.3 System Examples
      1. 8.3.1 Thermocouple Cold Junction Compensation
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Waterproofing Sensors
    4. 10.4 Mounting the Sensor at the End of a Cable
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Related Links
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

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.

8.2 Typical Application

569802.pngFigure 13. Basic Temperature Sensor

8.2.1 Design Requirements

Table 1. Design Parameters

PARAMETER EXAMPLE VALUE
Accuracy at 25°C ±1°C
Accuracy from –55 °C to 150 °C ±2.7°C
Forward Current 1 mA
Temperature Slope 10m V/K

8.2.2 Detailed Design Procedure

For optimum accuracy, R1 is picked such that 1 mA flows through the sensor. Additional error can be introduced by varying load currents or varying supply voltage. The influence of these currents on the minimum and maximum reverse current flowing through the LM135 should be calculated and be maintained in the range of 0.4 mA to 5 mA. Minimizing the current variation through the LM135 will provide for the best accuracy. The Operating Output Voltage Change with Current specification can be used to calculate the additional error which could be up to 1 K maximum from the LM135A, for example.

8.2.3 Application Curve

569829.pngFigure 14. Reverse Characteristics

8.3 System Examples

569810.pngFigure 15. Wide Operating Supply
569818.png
Wire length for 1°C error due to wire drop
Figure 17. Average Temperature Sensing
569805.pngFigure 19. Simple Temperature Controller
569822.png
Adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
Figure 21. Ground Referred Fahrenheit Thermometer
569824.png
To calibrate adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.
Figure 23. Fahrenheit Thermometer
569804.pngFigure 16. Minimum Temperature Sensing
569820.pngFigure 18. Isolated Temperature Sensor
569821.pngFigure 20. Simple Temperature Control
569823.png
Adjust for 2.7315V at output of LM308
Figure 22. Centigrade Thermometer

8.3.1 Thermocouple Cold Junction Compensation

569806.png
Compensation for Grounded Thermocouple
Select R3 for proper thermocouple type
Figure 24. Thermocouple Cold Junction Compensation
THERMO-COUPLE R3 (±1%) SEEBECK COEFFICIENT
J 377 Ω 52.3 μV/°C
T 308 Ω 42.8 μV/°C
K 293 Ω 40.8 μV/°C
S 45.8 Ω  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
THERMO-COUPLE R3 R4 SEEBECK COEFFICIENT
J 1.05K 385Ω 52.3 μV/°C
T 856Ω 315Ω 42.8 μV/°C
K 816Ω 300Ω 40.8 μV/°C
S 128Ω 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
569811.png
Select R3 and R4 for thermocouple type
Figure 25. Single Power Supply Cold Junction Compensation
569807.pngFigure 27. Differential Temperature Sensor
569813.png
Adjust D1 to 50 mV greater VZ than D2.
Charge terminates on 5°C temperature rise.
Couple D2 to battery.
Figure 29. Fast Charger For Nickel-Cadmium Batteries
569816.pngFigure 31. Ground Referred Centigrade Thermometer
569812.png
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.
Figure 26. Centigrade Calibrated Thermocouple Thermometer
569807.pngFigure 28. Differential Temperature Sensor
569815.png
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
Figure 30. Variable Offset Thermometer
569817.png
*Self heating is used to detect air flow
Figure 32. Air Flow Detector