SNIS192C November   2016  – June 2018 LMT01-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     LMT01-Q1 Accuracy
  3. 3 Description
    1.     2-Pin IC Temperature Sensor
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Electrical Characteristics
    6. 6.6  Electrical Characteristics - TO-92/LPG Pulse Count to Temperature LUT
    7. 6.7  Electrical Characteristics - WSON/DQX Pulse Count to Temperature LUT
    8. 6.8  Switching Characteristics
    9. 6.9  Timing Diagram
    10. 6.10 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 Output Interface
      2. 7.3.2 Output Transfer Function
      3. 7.3.3 Current Output Conversion to Voltage
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Mounting, Temperature Conductivity, and Self-Heating
    2. 8.2 Typical Application
      1. 8.2.1 3.3-V System VDD MSP430 Interface - Using Comparator Input
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Setting the MSP430 Threshold and Hysteresis
        3. 8.2.1.3 Application Curves
    3. 8.3 System Examples
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    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

8.1.1 Mounting, Temperature Conductivity, and Self-Heating

The LMT01-Q1 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface to ensure good temperature conductivity. The temperatures of the lands and traces to the leads of the LMT01-Q1 also affect the temperature reading, so they must be a thin as possible.

Alternatively, the LMT01-Q1 can be mounted inside a sealed-end metal tube, and then can be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LMT01-Q1 and accompanying wiring and circuits must be kept insulated and dry to avoid excessive leakage and corrosion. Printed-circuit coatings are often used to ensure that moisture cannot corrode the leads or circuit traces.

The junction temperature of the LMT01-Q1 is the actual temperature being measured by the device. The thermal resistance junction-to-ambient (RθJA) is the parameter (from Thermal Information) used to calculate the rise of a device junction temperature (self-heating) due to its average power dissipation. The average power dissipation of the LMT01-Q1 is dependent on the temperature it is transmitting as it effects the output pulse count and the voltage across the device. Equation 4 is used to calculate the self-heating in the die temperature of the LMT01-Q1 (TSH).

Equation 4. LMT01-Q1 Equation_03_SH_SNIS189.gif

where

  • TSH is the ambient temperature
  • IOL and IOH are the output low and high current level, respectively
  • VCONV is the voltage across the LMT01-Q1 during conversion
  • VDATA is the voltage across the LMT01-Q1 during data transmission
  • tCONV is the conversion time
  • tDATA is the data transmission time
  • PC is the output pulse count
  • RθJA is the junction to ambient package thermal resistance

Plotted in the curve Figure 21 are the typical average supply current (black line using left y axis) and the resulting self-heating (red and violet lines using right y axis) during continuous conversions. A temperature range of –50°C to +150°C, a VCONV of 5 V (red line) and 2.15 V (violet line) were used for the self-heating calculation. As can be seen in the curve, the average power supply current and thus the average self-heating changes linearly over temperature because the number of pulses increases with temperature. A negligible self-heating of about 45m°C is observed at 150°C with continuous conversions. If temperature readings are not required as frequently as every 100 ms, self-heating can be minimized by shutting down power to the part periodically thus lowering the average power dissipation.

LMT01-Q1 C001_SNIS189.pngFigure 21. Average Current Draw and Self-Heating Over Temperature