SBOA600 July   2024 ISOTMP35

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Calculating Thermal Response Time
    2. 1.2 Current Design with Non-Isolated Temperature Sensors
    3. 1.3 Proposed Design Using the ISOTMP35 Isolated Temperature Sensor
  5. 2Experiment Setup
    1. 2.1 Step 1: Prepare the Oil Bath
    2. 2.2 Step 2: Prepare the Liquid Gallium
    3. 2.3 Step 3: Submerge the Copper Pad
    4. 2.4 Step 4: Prepare Each PCB Configuration
    5. 2.5 Step 5: Testing Each PCB Configuration
    6. 2.6 Test Results
  6. 3Summary
  7. 4References

2.6 Test Results

After running all three tests on two boards each, the results were averaged together for each test. The results show that ISOTMP35 has a significantly faster temperature response time compared to either NTC option, with an average response time of 3.127 seconds. This is a factor of 10x better than even the NTC with thermal epoxy. Also worth noting that despite the NTC being in a much smaller package (which can provide a lower thermal mass and hence better thermal response time), the much larger ISOTMP35 is much faster.

ISOTMP35 achieves an average final temperature of 72°C. In this experiment, it is not able to achieve 75°C because the ISOTMP35 is fully exposed to the air during the test, which is 25°C. The ISOTMP35 is thermally coupled to the copper pad, but the cooler air temperature still drags the final achievable final temperature. This is still a significant improvement over an NTC, which was not able to exceed 66°C even with thermal epoxy.

Table 2-1 Response Time and Final Temperature Achieved Summary
DUTTemp Response Time #1 (seconds)Temp Response Time #2 (seconds)AVG temp response time (seconds)Final achieved temperature #1 (°C)Final achieved temperature #2 (°C)AVG final achieved temperature (°C)
ISOTMP353.1s3.1s3.1s72.2°C71.9°C72.1°C
NTC no epoxy74.9s81.6s78.3s61.7°C62.5°C62.1°C
NTC with epoxy47.2s48.3s47.8s65.8°C63.9°C64.9°C
Temperature Response Time ResultsFigure 2-9 Temperature Response Time Results