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

6.2 TMP6 Thermistor Standard Component Footprints

The TMP6 thermistors are currently available in a X1SON (DEC), SOT-5X3 (DYA) and TO-92S (LPG) packages. The DYA package sits on an IPC-782A 0603 footprint with no issues to fit or solder quality. TI recommends to reduce the pads if possible to minimize excess copper to achieve the maximum sensitivity of the part. However it’s not necessary to change the foot print at all. The size of the footprint has no bearing on the accuracy of the part. Also note that the IPC recommends increasing the land pad size to increase robustness in wave soldering. This is good for this device when using a standard 0603 pad size.

GUID-E6F79578-8F0C-4A58-B37B-54F948F275EE-low.pngFigure 6-2 TMP6 DYA Package on IPC-782A 0603 Footprint.

While the data sheet highlights the SOT-5X3/DYA package being 0603/1608 footprint-compatible, it is also compatible with the 0805/2012 footprint due to its unique lead frame dimensions.

GUID-8ECB303B-CB74-428B-873A-2846FCB807F9-low.pngFigure 6-3 TMP6 Thermistor DYA on IPC-782A-0805 Footprint.

When the DYA, IPC 0603 and IPC 0805 PCB footprints are overlaid, as shown in image below, it can be seen that the recommended PCB foot print for the DYA has a slightly larger space recommendation than the 0603/1608 or the 0805/2012. The important part to observe in this comparison is to ensure the heel of the TMP6 thermistor pins, as landed on the 0805/2012 pads will allow for the required heel fillet according to the IPC-A-610G standards (for solder quality). The toe and side fillets will easily meet the same IPC-A-610G requirements with the larger pad size that the 0805/2012 footprint presents as compared to either the 0603/1608 or the DYA footprint.

Additional details can be found on the e2e forum in the TMP61 Thermistor FAQ here.