SNOSD82D June   2018  – September 2022 TMP117

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 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Two-Wire Interface Timing
    8. 6.8 Timing Diagram
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Power Up
      2. 7.3.2 Averaging
      3. 7.3.3 Temperature Result and Limits
    4. 7.4 Device Functional Modes
      1. 7.4.1 Continuous Conversion Mode
      2. 7.4.2 Shutdown Mode (SD)
      3. 7.4.3 One-Shot Mode (OS)
      4. 7.4.4 Therm and Alert Modes
        1. 7.4.4.1 Alert Mode
        2. 7.4.4.2 Therm Mode
    5. 7.5 Programming
      1. 7.5.1 EEPROM Programming
        1. 7.5.1.1 EEPROM Overview
        2. 7.5.1.2 Programming the EEPROM
      2. 7.5.2 Pointer Register
      3. 7.5.3 I2C and SMBus Interface
        1. 7.5.3.1 Serial Interface
          1. 7.5.3.1.1 Bus Overview
          2. 7.5.3.1.2 Serial Bus Address
          3. 7.5.3.1.3 Writing and Reading Operation
          4. 7.5.3.1.4 Slave Mode Operations
            1. 7.5.3.1.4.1 Slave Receiver Mode
            2. 7.5.3.1.4.2 Slave Transmitter Mode
          5. 7.5.3.1.5 SMBus Alert Function
          6. 7.5.3.1.6 General-Call Reset Function
          7. 7.5.3.1.7 Timeout Function
          8. 7.5.3.1.8 Timing Diagrams
    6. 7.6 Register Map
  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
        1. 8.2.2.1 Noise and Averaging
        2. 8.2.2.2 Self-Heating Effect (SHE)
        3. 8.2.2.3 Synchronized Temperature Measurements
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2.2 Self-Heating Effect (SHE)

During ADC conversion, some power is dissipated that heats the device despite the small power consumption of the TMP117. Consider the self-heating effect (SHE) for certain precise measurements. Figure 8-2 shows the device SHE in still air at 25 °C after the supply is switched on. The device package is soldered to the 11-mm × 20-mm × 1.1-mm size coupon board. The board is placed horizontally, with the device on top. The TMP117 is in continuous conversion mode with 64 sampling averaging and zero conversion cycle time. There is no digital bus activity aside from reading temperature data one time each second. As shown in Figure 8-2, the SHE stabilization time in still air is greater when the device dissipates more power.

The SHE drift is strongly proportional to the device dissipated power. The SHE drift is also proportional to the device temperature because the consumption current with the same supply voltage increases with temperature. Figure 8-3 shows the SHE drifts versus temperature and dissipated power at 25 °C for the same coupon board and the same conditions described previously.

To estimate the SHE for similar size boards, calculate the device consumption power for 25 °C and use the corresponding power line shown in Figure 8-3. For example, in CC mode without DC at a 3.3-V supply at 25 °C, the device dissipates 410 µWt. So self-heating in still air is approximately 40 m°C for the described condition and rises to 52 m°C at 150 °C.

The following methods can reduce the SHE:

  • System calibration removes not only the self-heating error and power-supply rejection ratio (PSRR) effect but also compensates the temperature shift caused by the thermal resistance between the device and the measured object.
  • If practical, use the device one-shot mode. If continuous conversion is needed, use the conversion cycle mode with significant standby time. For example, in most cases an 8-sample averaging (125 ms) with a 1-second conversion cycle provides enough time for the device to cool down to the environment temperature and removes the SHE.
  • Use the minimal acceptable power supply voltage.
  • Use a printed-circuit board (PCB) layout that provides minimal thermal resistance to the device.
  • Avoid using small-value pullup resistors on the SDA and ALERT pins. Instead, use pullup resistors larger than 2 kΩ.
  • Ensure that the SCL and SDA signal levels remain below 10% or above 90% of the device supply voltage.
  • Avoid heavy bypass traffic on the data line. Communication to other devices on the same data line increases the supply current even if the device is in SD mode.
  • Use the highest available communication speed.