SBOU246 January   2022 TMP61 , TMP61-Q1 , TMP63 , TMP63-Q1 , TMP64 , TMP64-Q1

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 NTC Thermistor Versus TMP6 Linear Thermistor Family
    2. 1.2 NTC/Linear Thermistor TCR
    3. 1.3 NTC Versus Silicon-Based Linear Thermistor Trade-Offs
    4. 1.4 TMP6 Accuracy
  3. 2Typical NTC Thermistor Design Considerations
    1. 2.1 Voltage-Biased NTC Thermistor Network
    2. 2.2 Pinouts/Polarity
    3. 2.3 Converting NTC Thermistor Hardware Design to TMP6 Linear Thermistor Design
    4. 2.4 Simple Look-Up Table
  4. 3Software Changes
    1. 3.1 Firmware Design Considerations
    2. 3.2 Oversampling
    3. 3.3 Low-Pass Filtering in HW Versus SW
    4. 3.4 Calibration
  5. 4Design considerations for Full-Scale Range Voltage Output
    1. 4.1 Simple Current-Biased
    2. 4.2 Active Voltage-Biased
  6. 5Conclusion
  7. 6Additional Resources/Considerations
    1. 6.1 Constant-Current Source Design
    2. 6.2 TMP6 Thermistor Standard Component Footprints
    3. 6.3 Dual-Sourcing Approach for TMP6 and NTC Thermistors

Converting NTC Thermistor Hardware Design to TMP6 Linear Thermistor Design

For a simple NTC thermistor design, the converting from an NTC thermistor to the TMP6 Linear Thermistor is straightforward. The only hardware change is to swap the NTC thermistor and the TMP61 thermistor, while RBIAS can be left as is. The resulting transformation can be seen in Figure 2-4 below.

GUID-20210628-CA0I-HVPW-NWKW-NLRTT1B8ZFRS-low.gifFigure 2-4 TMP6 Linear Thermistor Voltage Divider Circuit

The circuit above results in the following voltage response. Notice how the voltage response is positive.

GUID-7FBE350C-F79E-402E-B641-EE9A983F8B67-low.pngFigure 2-5 TMP6 Linear Thermistor Positive Voltage Response.

A positive voltage response can be used for new designs, but matching a negative response that the original NTC thermistor circuit generated may be useful for old designs. To provide a negative voltage response with the TMP6 Linear Thermistor, the bias resistor and TMP6 Linear Thermistor must switch positions. After redesigning, you can see the resulting negative voltage response below.

Figure 2-6 TMP6 Linear Thermistor Circuit for Negative Voltage Response.

GUID-891C0F2C-73B1-4D2B-B5D3-383E647ACDB4-low.pngFigure 2-7 TMP6 Linear Thermistor Negative Voltage Response.